a framework for assessing the environmental water

A Framework for assessing the

Environmental Water Requirements of

Groundwater Dependent Ecosystems

REPORT 3 IMPLEMENTATION

Prepared for

Land & Water Australia

Level 1, Phoenix Building86 Northbourne AvenueBRADDON ACT 2612

27 April 2007

Document Title

Project REM1 - A Framework for assessing the Environmental Water Requirements of Groundwater Dependent Ecosystems Report 3 Implementation

Document Author(s)

Paul Howe Resource & Environmental Management Pty Ltd Jodie Pritchard Resource & Environmental Management Pty Ltd

Contributing Author(s)

Peter Cook CSIRO Land and Water Rick Evans Sinclair Knight Merz Pty Ltd Craig Clifton Sinclair Knight Merz Pty Ltd Marcus Cooling Ecological Associates Pty Ltd

Distribution List

Copies Distribution Contact Name 1 LWA Brendan Edgar 2 Steering committee Craig Simmons; Steve Gatti 3 Project Team Rick Evans; Peter Cook; Paul Howe 1 REM Library Anya O’Regan

Document Status

Doc. No. DB01-R004 Approved for Issue

Rev No. Name Signature Date

Project manager Paul Howe C Peer review Rick Evans

23/04/07

Resource & Environmental Management Pty Ltd ABN 47 098 108 877 Suite 9, 15 Fullarton Road, KENT TOWN SA 5067 Telephone: (08) 8363 1777 Facsimile: (08) 8363 1477

Sandy Creek, Pioneer Valley, Queensland (Qld. Dept. Natural Resources and Water)

Coolabah Woodland, Mt Bruce Flats, Pilbara Region, Western Australia (P Howe)

Wetland, South East, South Australia (South East NRM Board)

A national framework for assessing the EWRs of GDEs – Report 3

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Table of Contents

1 INTRODUCTION............................................................................................ 1

1.1 Overview of the National Framework for assessing the environmental water requirements of groundwater dependent ecosystems 1

1.2 The Framework report 2 1.3 Report format 2

2 BACKGROUND ............................................................................................. 4

2.1 Groundwater dependent ecosystems 4 2.1.1 What is a GDE? 4 2.1.2 Types of GDEs to be assessed by the framework 4

2.2 Water planning 5 2.3 Prior work 7

3 TOOLBOX SUMMARY .................................................................................. 8

4 FRAMEWORK ............................................................................................... 9

5 STEP 1; SETTING THE CONTEXT ............................................................. 13

5.1 Overview 13 5.2 Step 1.1; Defining study objectives and scope 14 5.3 Step 1.2; Identifying biophysical setting 15 5.4 Step 1.3; Identifying potential GDEs 17 5.5 Step 1.4; Setting ecological objectives 21

6 STEP 2; IDENTIFYING PROCESSES........................................................ 25

6.1 Overview 25 6.2 Step 2.1; Establish relationships between GDEs & their hydrological environment 26 6.3 Step 2.2; Threat analysis 45 6.4 Step 2.3; Environmental response functions 47 6.5 Step 2.4; Derive/refine EWRs for GDEs 52

7 MONITORING AND EVALUATION ............................................................. 54

7.1 Monitoring 54 7.2 Evaluation 54

8 REFERENCES............................................................................................. 55

9 GLOSSARY OF TERMS.............................................................................. 59


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List of Tables, Figures, Plates, Appendices TABLES

Table 3.1 Toolbox summary Table 5.1 GDE studies – needs vs. available budgets Table 5.2 Tools for identifying linkages between GDEs and the landscape Table 5.3 Tools for identifying potential GDEs Table 5.4 Tools for setting ecological objectives Table 6.1 Tools to assist in establishing relationships between terrestrial GDEs &

groundwater Table 6.2 Tools to assist in establishing relationships between stream baseflow and wetland

GDEs Table 6.3 Tools to assist in threat analysis

FIGURES

Figure 2.1 Hypothetical GDE response function. Water availability, in this context, will relate as much to condition (e.g. level, flux and quality) as to volume.

Figure 2.2 The GDE function lag-time concept in response to altered groundwater availability. The solid line shows the decline in groundwater availability over time (e.g. due to lower water tables or reduced baseflows), whilst the dashed line shows the lagging condition response of a GDE to the changed groundwater conditions.

Figure 4.1 A framework for assessing the environmental water requirements of GDEs Figure 4.2 The broader water planning framework for assessing GDE EWRs Figure 5.1 Step 1 of the Framework, which involves setting the context for GDE studies. Figure 6.1 Step 2 of the Framework, which identifies GDE water requirements, as well as

assessing how water affecting activities might impact on ecological function.

CASE STUDIES

Case Study 1 Conceptual model development Case Study 2 Identifying potential wetland GDEs Case Study 3 Development of ecological objectives for GDEs Case Study 4 Water balance modeling Case Study 5 Use of water potentials and stable isotopes in assessing terrestrial vegetation

dependence on groundwater Case Study 6 Identifying baseflow contribution to rivers Case Study 7 The use of tracers in assessing groundwater baseflow to streams and rivers Case Study 8 Phreatophyte response to reduced water availability Case Study 9 Plant water use model for developing phreatophytic terrestrial vegetation response

functions


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APPENDICES

Appendix A Existing Frameworks, policies and methods


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1 INTRODUCTION

1.1 Overview of the National Framework for assessing the environmental water requirements of groundwater dependent ecosystems

The primary purpose of water allocation planning in Australia is to achieve an equitable way in which to allocate and manage a region’s water resources that is consistent with the Council of Australian Government’s (COAG) Water reform framework (COAG, 1994), and to protect the characteristics of ecosystems that are considered important to their function (services provided) and conservation value. To do this, the needs of all water users have to be considered in water planning policy, including those of communities and ecosystems.

Typically, the needs of ecosystems dependent on surface water systems are routinely addressed within the various national approaches to water allocation planning. However, this is not often the case for groundwater dependent ecosystems (GDEs), which are natural ecosystems that require access to groundwater to meet all or some of their water requirements so as to maintain their communities of plants and animals, ecological processes and ecosystem services. Their environmental water requirement (EWR) is defined as the water regime needed to maintain a particular composition, structure and level of ecological function and ecosystem service provision. Often, the natural water regime of GDEs will comprise of a combination of one or more of groundwater, surface water and soil water.

An existing conceptual framework for GDE management devised for Australia in 2001 (Clifton and Evans, 2001) comprises of four steps: (i) identify potential GDEs; (ii) establish the natural water regime of GDEs and their level of dependence on groundwater; (iii) assess the EWRs of GDEs; and (iv) devise the necessary water provisions for GDEs. However, work undertaken to date in Australia to provide water for GDEs has generally stalled at the identification stage and has not progressed through the three remaining steps of the 2001 conceptual framework. Consequently, EWRs have generally been subjectively derived and are based on ‘best estimates’ of ecosystem interactions with groundwater. EWRs that have been determined in this way provide only limited confidence that any later environmental water provision (EWP) will actually sustain ecosystem function.

Consequently, there is an identified need to develop a National Framework for assessing the EWRs of GDEs so as to provide a platform from which to take advantage of current and future information concerning phreatophytic (terrestrial), wetland and stream baseflow GDEs and assist water resource, catchment and ecosystem managers, or their advisors, in making consistent and effective management decisions for those ecosystems.

Development of the National Framework for assessing the EWRs of GDEs has involved:

1. compilation of the existing set of methods (tools) available for identifying GDEs and quantifying their interaction with groundwater, as well as other water sources such as soil and surface water (Report 1);

2. undertaking field studies to further test / assess the ability of tools presented in the Toolbox to predict ecosystem response mechanisms to altered water regimes


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(environmental response functions; ERFs) and to ascertain their applicability throughout Australia (Report 2); and

3. development of an assessment framework that can be consistently applied at a national level to assist water resource, catchment and ecosystem managers, or their advisors, in the determination of EWRs (Report 3).

1.2 The Framework report This report presents the National Framework for the assessment of EWRs of GDEs. It has been designed to assist water resource, catchment and ecosystem managers, or their advisors, in considering the needs of GDEs in water allocation planning policy. A key objective of the overall Framework is to provide a basis to assist in moving the determination of EWRs beyond the traditional desktop approach to more advanced and definitive approaches that might involve field investigations and testing, as well as modeling.

Key considerations in providing for ecosystem EWRs include the timing of water availability, the manner in which water is made accessible, and the source of the water on which ecosystem function or conservation value depends. Consequently, the Framework is designed to follow a series of logical steps moving from the GDE identification phase right through to EWR determination.

1.3 Report format The Framework report outlines the proposed methodology for deriving EWRs for ecosystems dependent on groundwater. The report is structured as follows:

Section 1 Introduction Presents an introduction to the Framework including a brief overview of objectives and scope.

Section 2 Project overview Provides an introduction to the types of GDEs to be addressed by the Framework, water planning activities and background information.

Section 3 Toolbox Presents a brief summary of the toolbox that is available to assist catchment managers in developing a knowledge base from which to derive EWRs. Report 1 (Clifton et al, 2007) provides more detail.

Section 4 Framework Presents the Framework, including an overview of the two important steps involved in deriving EWRs and a flowchart showing linkages between the various components of the Framework.

Section 5 Step 1; Setting the context Outlines the types of studies required to set the context for any project required to derive EWRs for GDEs, commencing with defining objectives and scope, and then identifying the linkages between landscape, ecosystems and groundwater, and defining ecological objectives, and provides brief summaries of relevant case studies.


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Section 6 Step 2; Identifying processes Outlines the types of studies that can be undertaken to identify processes governing the interaction between GDEs and water regimes within which, and on which, they exist and depend. Provides an outline of key steps from which to derive or refine EWRs, and provides brief summaries of relevant case studies.

Section 7 Monitoring and evaluation Provides an overview of the role of monitoring and evaluation within the Framework and water management policy.

Section 8 References A list of references, including published literature and Government reports relating to GDEs and EWR determination.

Section 9 Provides a glossary of terms used in this report.

Appendices Supporting information regarding existing frameworks and methodologies.


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2 BACKGROUND

2.1 Groundwater dependent ecosystems

2.1.1 What is a GDE? GDEs include wetlands and forests, as well as springs and rivers. What distinguishes GDEs from other types of ecosystems is that they rely on groundwater for some, or all, of their water requirements. For example:

• a forest, where some or all of the plant species draw water from near the water table (i.e. the capillary fringe) for all or some of the year, is regarded as a GDE;

• aquatic vertebrates and invertebrates that rely on consistent water temperatures provided by groundwater baseflow to streams or springs for reproduction form part of a GDE; and

• a wetland that relies on a shallow water table during the dry season/summer is a GDE.

A GDE can be described as having obligate or facultative dependence on groundwater. Obligate dependence does not necessarily mean an ecosystem is totally dependent on, or requires continuous access to, groundwater, but does mean that groundwater forms a critically important water source at some stage in an ecosystem’s hydrological regime. Facultative dependence describes the situation where the presence or absence of groundwater is not crucial to the presence of species within an ecosystem, and that such factors as landscape position form the overriding constraint on the sources of water used. Eamus and Froend (2006) provide further discussion concerning obligate and facultative dependence.

A GDE’s access to groundwater can be critically important to maintaining ecosystem viability and biodiversity. Unfortunately, many GDEs Australia-wide have come under threat because access to groundwater resources has reduced where groundwater development (e.g. for agriculture, industry and potable supply) and land-use change has not been appropriately managed.

As already identified, the Framework focuses on terrestrial vegetation, inland wetlands and river baseflow ecosystems that require groundwater to maintain ecosystem function. It is acknowledged that groundwater is also an integral part of some aquifer, cave and coastal ecosystems, but these types of GDEs are not within the scope of this project.

2.1.2 Types of GDEs to be assessed by the framework Terrestrial GDEs include deep and / or shallow-rooted vegetation communities, and endemic fauna, whose use of groundwater is either obligatory or facultative.

Wetland GDEs can be either ephemeral or permanent wetland systems that have continuous or seasonal connection to groundwater. These types of GDEs include fringing and aquatic vegetation communities, subsurface refuges, as well as aquatic biota that depend on surface water expression of groundwater.


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Stream baseflow GDEs occupy or fringe both ephemeral and permanent flowing streams that have seasonal or continuous groundwater contribution to their water regimes, and also includes groundwater flowing through the hyporheic zone in the case of ephemeral streams.

2.2 Water planning Conservation and water planning policy often seeks to protect highly valued characteristics of ecosystems that are subject to change from human activity. This might involve taking steps to preserve all or only some of the species present within the ecosystem, or maintaining particular breeding or migration events, or preserving the extent of a particular species’ habitat. Describing ecosystem characteristics that are to be maintained establishes a set of ecological objectives that define these ecosystems in narrower terms, against which the success of conservation policy can be measured.

The primary purpose of water allocation planning in Australia is to achieve equitable and sustainable allocation and management of a region’s water resources, and to do so in a manner that is consistent with the Council of Australian Government’s (COAG) Strategic Framework for Water Reform. To do this, the needs of all users of the resource have to be considered, including those of the community and ecosystems. Typically, the needs of ecosystems dependent on surface water are routinely addressed within the national approach to water allocation planning, but this is not always the case for GDEs. Consequently, the GDE Framework will form an important component of any assessment of ecosystem water needs within an overarching water planning framework.

It is not easy (and often not technically correct) to provide a water allocation to GDEs purely on an annual basis or as a percentage share of available allocations because GDEs do not necessarily require access to groundwater on a continuous basis. Recently conducted studies have identified that the most important aspect of water allocation planning for GDE water provisions is the maintenance of ecosystem access to groundwater at critically important times (e.g. Howe et al., 2006).

Figure 2.1 shows the relationship, or GDE response function, between ecosystem function and water availability for a hypothetical GDE. Water availability, in this context, will relate as much to condition (e.g. level, flux, quality) as to volume. As illustrated:

• The current water regime available to GDEs may not necessarily be the natural regime (i.e. the one existing before human intervention). This water regime may comprise entirely of groundwater, or it may represent a “mixture” of groundwater, soil water and surface water.

• Many GDEs will likely tolerate a level of reduced water availability without suffering a decline in condition. However, below a certain point (threshold) the decline in ecosystem condition becomes more severe. If the ecosystem is not resilient, and this “threshold” is exceeded, the GDE may not recover even if water availability is returned to “normal”.

There are two important time lags in this response function (Figure 2.2): (i) the hydraulic response, relating to the time lag between commencement of groundwater abstractions (for example) and onset of drawdown at the location of interest; and (ii) the ecological time lag, relating to the timing of reduced water availability and ecosystem response.


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Figure 2.1 Hypothetical GDE response function. Water availability, in this context, will relate as much to condition (e.g. level, flux and quality) as to volume (adapted from Howe et al., 2006).

Figure 2.2 The GDE function lag-time concept in response to altered groundwater availability. The solid line shows the decline in groundwater availability over time (e.g. due to lower water tables or reduced baseflows), whilst the dashed line shows the lagging condition response of a GDE to the changed groundwater conditions (after Howe et al., 2006).


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2.3 Prior work Development of the Framework follows on from the experience gained from work undertaken only in the last ten years or so. The recognition that ecosystems reliant on groundwater need to be formally considered in the water planning and allocation process really commenced with the work of Hatton and Evans (1998), which involved a national-scale assessment of GDEs. This is not to say, however, that the water needs of GDEs had not previously been considered for infrastructure projects involving groundwater development. For example, assessing the impact of mine water supply development on possible phreatophytic vegetation had high priority for Rio Tinto in the early 1990s during development of the Marandoo Iron Ore Mine in the Pilbara Region of Western Australia (Hamersley Iron, 1992).

Important frameworks and guidelines following on from the work of Hatton and Evans include the National Conservation Council’s Desktop methodology to identify groundwater dependent ecosystems (NCC, 1999), and the National River Health Program’s Environmental water requirements to maintain groundwater dependent ecosystems (Clifton and Evans, 2001).

Appendix A presents brief details of some of the more important frameworks, policies and methods that have evolved since the late 1990s and have a particular focus on assessing GDE EWRs and management. These frameworks, policies and methods form the basis for the GDE Framework that has been developed here for Land & Water Australia, which has the key objective of provide a nationally consistent systematic approach, and scientific basis, for determining water related management decisions for ecosystems, and ultimately, the allocation of funds to assist in developing awareness and management strategies that are designed to protect GDEs.


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3 TOOLBOX SUMMARY

The toolbox is essentially a collection of tools that can be applied individually or as a group to identify GDE EWRs. They have been sourced from methods reported in national and international literature. Each tool comprises a description, the type of GDE it can be applied to, the scientific principles involved in using the tool and how it is applied in GDE assessments, as well as an indication of costs and limitations involved in using the tool. Table 3.1 provides an overview of the toolbox along with a brief description of each tool. Report 1 GDE Toolbox provides more detail concerning each tool.

Table 3.1 Toolbox summary

Code Tool Description

T1 Mapping tools Mapping of geology and geological structures, water table depth or aquifer pressure and the distribution, composition and / or condition of vegetation as a means of identifying ecosystems that are likely to have access to and use groundwater.

T2 Water balance techniques

Identify and quantify groundwater use by measurement or estimation of various components of an ecosystem’s water cycle.

T3 Pre-dawn leaf water potential

Pre-dawn leaf water potential measurements to identify groundwater use and depth of water uptake.

T4 Stable isotope analysis – vegetation

Comparison of the fractionation of isotopes in plant xylem water with potential source waters to identify groundwater uptake.

T5 System response to change

Long term monitoring of ecosystem composition and ecological function in response to management intervention, climate, and soil water, surface water and groundwater conditions.

T6 Groundwater - surface water hydraulics

Application of hydraulic principles, statistical analyses of stream hydrographs and site measurements to derive the degree of interaction between groundwater and surface water features.

T7 Physical properties of water

Measurement of water electrical conductivity and temperature change along the length of a river / wetland, or over time to identify a groundwater contribution.

T8 Analysis of water chemistry

Chemical analysis of surface water and groundwater for isotopes, major anions and cations, and trace elements. Mixing relationships identify groundwater contribution.

T9 Introduced tracers Use of introduced chemical tracers to observe mixing and dilution relationships and assess the contribution of groundwater to a stream.

T10 Plant water use modelling

Mathematical representations (or models) of plant water balance to estimate plant water requirements and / or groundwater uptake, and / or response to water table drawdown.

T11 Groundwater modelling

Two or three-dimensional mathematical representations (or models) of water movement in the saturated and unsaturated zones to assess the potential level of interaction between groundwater and surface water bodies and between groundwater and terrestrial ecosystems.

T12 Conceptual modelling

Use of expert knowledge of similar ecosystems, biophysical environments and relevant data to develop a conceptual model of the ecosystem and its interaction with groundwater.

T13 Root depth and morphology

Assessment of the depth and morphology of plant root systems, and comparison with measured or estimated water table depth to assess potential for groundwater uptake.

T14 Analysis of aquatic ecology

Use of ecological survey techniques to identify aquatic species with reproductive behaviour or habitat requirements that indicate groundwater dependency.


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4 FRAMEWORK

Figure 4.1 presents a summary of the proposed Framework for Assessing EWRs for GDEs. The Framework involves a logical progression of knowledge generation concerning GDEs for specific management areas that will assist water planners in moving through the four important phases of determining appropriate water allocations for GDEs, i.e.: (i) identify potential GDEs; (ii) establish GDE natural water regime and level of dependence; (iii) assess GDE EWRs; and (iv) devise necessary water provisions for GDEs.

Ecosystem water requirements can in most cases be considered as being dynamic, and it is not often that a surface ecosystem will be totally dependent on groundwater, exceptions include the Great Artesian Basin springs. Those surface ecosystems that demonstrate groundwater dependence in many cases also have a degree of dependence on surface water and soil water. Consequently, the GDE Framework needs to be applied alongside other national frameworks, guidelines and principles that are designed to address ecosystem water requirements.

In all, the Framework lists two basic steps that are involved in adequately identifying the EWRs of GDEs:

Step 1. Setting the context

Identifying ecosystems that potentially have some degree of dependence on groundwater and physical aspects of the landscape in which they exist.

Setting of ecological objectives

Preliminary analysis of risk posed to GDEs by altered water regimes.

Step 2. Identifying processes

Establish ecosystem dependence on groundwater and the form of that dependence.

Identify water affecting activities that have the potential to impact adversely on ecological function, as well as social and economic considerations.

The Framework is designed to provide the basis for catchment managers to determine, with the best science available, environmental water provisions (EWPs) for groundwater dependent ecosystems, and to establish effective monitoring and evaluation programs by which to assess the success of water allocation planning and management strategies. Figure 4.2 presents the broader context within which the GDE Framework is planned to operate.


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Figure 4.1 A framework for assessing the environmental water requirements of GDEs


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As shown in Figure 4.2 there are some over-arching principles and guidelines within which the assessment of EWRs for GDEs should take place. These include, for example:

• The National principles for the provision of water for ecosystems (ARMCANZ and ANZECC, 1996).

• A National framework for improved groundwater management in Australia (ARMCANZ, 1996).

• The Australian and New Zealand guidelines for fresh and marine water quality (ANZECC and ARMCANZ, 2000).

• The Comparative evaluation of environmental flow assessment techniques: best practice framework (Arthington et al., 1998).

Also, as indicated, the GDE Framework will form the basis for setting environmental targets (environmental water provisions; EWPs), and developing effective management plans that include a formal process for monitoring, evaluating and reporting so as to assist in assessing the success of management.

Figure 4.2 The broader water planning framework for assessing GDE EWRs


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The following sections describe in more detail each of three steps of the GDE Framework, and the operational methods that can be employed to assist in moving through the four phases of GDE assessment identified in Clifton and Evans (2001):

• Step 1 (Setting the context), which is essentially generic for the three types of GDEs considered in the Framework, is presented as Section 5.

• As there will be sometimes subtle and at other times obvious differences in the methods applied to assess GDE water requirements for the different types of GDEs (terrestrial, wetland and baseflow), Step 2 (Identifying processes) addresses terrestrial GDEs separately from wetland and baseflow GDEs (Sections 6).


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5 STEP 1; SETTING THE CONTEXT

5.1 Overview An important aspect of developing environmental water provisions for GDEs is development of an understanding of the interaction between GDEs and their physical environment, particularly the hydrological, geological, soils and hydrogeological setting, and how these constrain the nature of ecosystem dependence on groundwater. Once the biophysical setting is understood:

• an understanding of the effects of groundwater development on GDEs can be better established; and

• effective management strategies can be implemented to manage adverse effects of groundwater development on ecosystem function.

Moving beyond the desktop approach to assessing GDE water requirements, developing more advanced and definitive approaches, through use of the toolbox (Report 1) will be important in achieving these outcomes.

As identified earlier, GDE studies undertaken to date have often stalled at the desk-top GDE identification phase, and have utilised only a limited number, and probably the more obvious, of the tools available for the assessment of GDE water requirements (see Table 3.1, and Report 1 for more detail). Examples include mapping (T1), observed system response to altered water regimes (T5) and simple water balance techniques (T2).

Figure 5.1 presents a summary of Phase 1 of the Framework, and the following describes the different aspects of the critically important first steps.

Figure 5.1 Step 1 of the Framework, which involves setting the context for GDE studies.


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This component of the GDE Framework addresses:

• identification of study area and biophysical setting ;

• identification of potential GDEs;

• conservation value of potential GDEs;

• form of groundwater dependence.

5.2 Step 1.1; Defining study objectives and scope

Daily (1997) and other authors, for example Boyd and Banzhaf (2006) and Murray et al (2006), discuss the services (benefits) provided by ecosystems, including GDEs. Example services include: (i) purification of air and water; (ii) mitigation of floods and droughts; (iii) maintenance of soil fertility; (iv) nutrient recycling; (v) detoxification and decomposition of wastes; (vi) crop and remnant vegetation pollination; (vii) pest and weed control; and (viii) recreation. Biodiversity maintenance is integral to continued provision of ecosystem services and, in the case of GDEs, biodiversity may be threatened by diversion of groundwater (and other water) resources away from important ecosystems.

The commencement of studies concerning ecosystem dependence on groundwater often begins with an identified need for groundwater resource management. More often than not, this need for management occurs after groundwater systems and, possibly, ecosystems have been placed under stress by development. Exceptions, however, exist for types of industry that tend to be more regulated by Government or that receive more community attention early in the development cycle, eg. mining and large-scale irrigation developments, where an assessment of ecosystem water needs often takes place before development occurs. For example, environmental monitoring and reporting programs undertaken in support of iron ore mining operations in the Pilbara region of Western Australia have considered the impact of mine water supply development and dewatering on groundwater dependent ecosystems at least since the early-1990s (BHP, 1995 and Hamersley Iron, 1992).

The definition of study objectives for GDEs will largely be constrained by four important factors: (i) the size (and age) of a development, particularly in relation to volumes of groundwater (or surface water) diversions, or the scale of other water affecting activities; (ii) proximity of a development to potentially sensitive ecosystems; (iii) the conservation value of the potentially sensitive ecosystems; and (iv) available budgets and study timeframes.

In a sense, defining the objectives of a study involving the assessment of GDE water requirements can take the form of a preliminary risk assessment, where:

• the consequence of groundwater development needs to be considered in light of the conservation significance of potential GDEs (e.g. biodiversity and ecological services provided); and

STEP 1.1

Defining study purpose and scope

Purpose: This component of the framework is required to clearly establish the bounds within which a particular GDE assessment is to take place, thereby ensuring appropriate levels of resourcing and funding are available to successfully conclude the study.


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• threat posed to GDEs needs to be described in terms of the degree to which water affecting activities will impact on groundwater conditions and likelihood of reduced water availability.

The most important overriding constraint in assessing GDE water requirements will often be the budgets that are available to conduct the necessary field investigations, undertake the necessary analyses and reporting, and establish appropriate management and evaluation programs. This is certainly the experience in most parts of Australia. Table 5.1 presents an overview of budgets that would typically be required for different levels of GDE studies, which will ideally be determined on the basis of a preliminary risk assessment.

Table 5.1 GDE studies – needs vs. available budgets

Level Description Budget range

Basic • Identification of potential GDEs, and preliminary management outcomes

<$30,000

Moderate • Identification of potential GDEs, provision of mapping products

• Relationship between ecosystem function and groundwater availability

• Conceptual management outcomes derived on basis of GDE water requirements

$20,000 - $100,000

Comprehensive • Identification of potential GDEs, provision of mapping products

• Relationship between ecosystem function and groundwater availability

• Understanding of ecosystem response to altered water regimes

• Detailed management outcomes that consider dynamic relationship between GDEs and natural water regimes

>$100,000

Notes: 1. indicative budgets only, and do not include costs associated with meetings and consultation exercises

5.3 Step 1.2; Identifying biophysical setting

An important component of establishing the context within which groundwater use by ecosystems takes place is the development of an understanding of the physical variables that support this dependence, for example geology, hydrology, climate, depth to groundwater and landscape position. Table 5.2 presents an overview of the tools best able to contribute to an understanding of the linkages between landscape and GDEs, and an overview of methods that can be employed in applying the tools.

STEP 1.2

Identifying biophysical setting

Purpose: To adequately assess the EWR of GDEs it will first be necessary to understand the way in which the ecosystem interacts with physical aspects of the landscape in which it occurs.


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Table 5.2 Tools for identifying linkages between GDEs and the landscape

Code Tool Example methods

T1 Mapping GIS mapping techniques also provide a very powerful tool for developing an understanding of the inter-relationship between potential GDEs and landscape features that may impact on water availability.

• Geology; Relating the location of potential GDEs with geological attributes of the study area can provide an understanding of the types of inter-relationships between ecosystems and groundwater, and possible issues relating to management. For example: (i) fractured rock aquifers may give rise to discrete springs that feed wetland or baseflow GDEs, whilst groundwater discharge to wetlands and baseflow systems from sedimentary aquifers may be more diffuse; and (ii) pumping from sedimentary and fractured rock aquifers may impact differently on the water table, e.g. in terms of drawdown patterns.

• Hydrogeology; Hydrographs provide a preliminary basis for recognising the range in water table depths (in the case of terrestrial GDEs) and elevations (in the case of wetland and stream baseflow GDEs) that form the “normal” water regime of different GDEs. In effect, this contributes to an early understanding of the EWRs of GDEs by establishing thresholds within which GDEs operate. Recharge data can also provide preliminary information concerning the likelihood of groundwater dependence, especially when taken in consideration of soil characteristics. The relationship between potential GDEs and groundwater flow systems is also an important consideration when assessing the scale of effect of water affecting activities.

• Soils; Soils data can be very informative in regard to GDE occurrence and the degree of groundwater dependence. Duplex soils can give rise to perched water tables, and where these occur associated ecosystems cannot be truly regarded as groundwater dependent, and maintenance of their ecological function will often mean developing different management strategies to what would normally be employed for GDEs. However, management of perched aquifer dependent ecosystems still needs to consider groundwater. In the case of terrestrial vegetation and ephemeral wetlands, soil water moisture may be the most important plant water source as less energy is expended on drawing water from the vadose zone (when it is abundant enough) than from the water table. Plant available water capacity (PAWC; mm) describes that amount of water in the vadose zone that is available for plant use. Typically, a large PAWC can be expected to correspond to a lower degree of reliance on groundwater. Factors affecting PAWC include soil type / texture and depth of vadose zone.

• Hydrology; Important considerations when assessing groundwater dependence by riparian vegetation is whether particular stream reaches are losing or gaining, and how baseflow contribution higher in a stream reach may contribute to maintenance of riparian vegetation in lower losing stream reaches. Comparison of groundwater hydrographs and stream stage can assist in developing an understanding of the gaining / losing nature of a stream.


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Table 5.2 Tools for identifying linkages between GDEs and the landscape (cont.)

Code Tool Example methods T2 Water

balance Simple water balance approaches can be undertaken to consider the degree to which vegetation or wetlands, for example, may be dependent on groundwater. These types of water balances may rely on one or more of the following data requirements.

• Climate; Seasonality and rates of annual rainfall and evaporation.

• Hydrogeology; Recharge rates, and position in landscape, e.g. recharge or discharge areas.

• Soils; Plant available water capacity (PAWC).

T13 Root depth and morphology

If available, information concerning the rooting depth of terrestrial and riparian vegetation can provide an indication of whether vegetation may be accessing groundwater to meet some of its water requirements. Canadell et al (1996) presents a selection of the maximum reported rooting depths of Australian plants.

5.4 Step 1.3; Identifying potential GDEs

This step in the Framework is not directly linked to determining EWPs for GDEs, but is a critical first step in identifying their EWRs as it establishes boundaries around future studies designed to more closely assess ecosystem interaction with groundwater.

This step involves assessing ecosystem groundwater dependence in an essentially remote and generic manner, although there may be subtle differences between the approaches taken to assess the three types of GDEs covered by this Framework. Interaction between an ecosystem and groundwater can take two forms:

• Direct interaction, where plants and animals use or consume water directly from the aquifer. In these situations, direct interaction will result in short-term response to altered water regimes (quantity and quality). These types of interaction are most readily recognised, and include plants that access groundwater (or the capillary fringe) to support all or some of their water requirements, and fauna having an aquatic habitat that relies on groundwater discharge.

• Indirect interaction, where plants and animals interact with other species having a direct relationship with groundwater. These types of interactions can be complex but subtle, and the consequence of altered natural water regimes may not be readily apparent or discernable from other variables such as pest and weed invasion. These subtle dependencies can influence food, nutrient and physical habitat throughout an entire ecosystem, both groundwater dependent and non-dependent components.

Once potential GDEs have been identified, it will be necessary to begin their categorisation, for example are they best defined as terrestrial, baseflow or wetland GDEs, and what is their

STEP 1.3

Identifying potential GDEs Purpose: To initiate an assessment process that efficiently addresses the type and nature of interaction between GDEs and their natural water regime.


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ecological (or conservation) significance? This leads directly into Step 2 (Identifying processes) but also allows ecological objectives and indicators to be identified that assist in ongoing evaluation of water management policy and strategies.

An assessment of conservation significance can utilise resources such as Environment Australia’s A directory of important wetlands in Australia, listings under the Commonwealth Environment Protection and Biodiversity Conservation (EPBC) Act, State environmental agency listings, Conservation Parks and Heritage agreements, and local experience.

A number of techniques can be applied to identify potentially groundwater dependent vegetation communities, wetlands and stream baseflow systems, depending on the availability of specific datasets. Table 5.3 presents an overview of the available tools and methods for identifying potential terrestrial GDEs.

Vegetation mapping or remotely sensed images (satellite images, air photographs) can be used to show the spatial distribution of ecosystems. In addition, knowledge or inference of groundwater dependence from occurrences of particular ecosystems can be extrapolated to other locations to identify potential GDEs.

Inference of groundwater dependence based on vegetation mapping, depth to water and leaf area index (LAI) may be supported by geomorphic or geological mapping, and any historic observations concerning system response to change.

Due to the inherent similarities between the form of groundwater dependence exhibited by some stream baseflow and wetland ecosystems the preliminary GDE identification process will essentially be the same. There are many components to baseflow and wetland ecosystems that potentially require access to groundwater for sustaining long-term ecosystem function, they may require periodical expression of groundwater at the surface, but in some instances surface expression may not be critical whereas having access to shallow groundwater to sustain fringing vegetation or maintain subsurface refuges during dry seasons / droughts is.

Table 5.3 Tools for identifying potential GDEs

Code Tool Example methods Suitable for GDE type

T1 Mapping Mapping, supported by GIS technology, provides a very powerful tool for developing an understanding of the inter-relationship between ecosystems and groundwater availability.

• Ecosystem location; The first mapping exercise in any GDE study should involve developing spatial relationships between ecosystems (remnant terrestrial, wetland and riparian vegetation) and potential water affecting activities (e.g. pumping, irrigation, diversions, drainage, reafforestation and vegetation clearing).

• Leaf area index (LAI); LAI is a measure of the leaf area per unit of ground surface. It is one of the most important parameters for determining the behaviour and productivity of ecosystems (source: Environment Canada). LAI provides a basis for establishing a relationship between ecosystem function and groundwater availability, as two outcomes of water stress are a reduction in leaf area and, as a result, lower rates of photosynthesis. High sustained LAI in an arid environment would suggest secure plant water availability.

Terrestrial vegetation, Baseflow, Wetland


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Table 5.3 Tools for identifying potential GDEs (cont.)

Code Tool Example methods Suitable for GDE type

• Greenness and thermal infra-red; Greenness is a measure of the status of photosynthesis in sampled vegetation communities, where a sustained high greenness index in arid environments especially, suggests secure plant water availability. Thermal infra-red is a measure of the temperature of plants, “cooler” temperatures will typically signify high rates of transpiration.

• Depth to water table; Ecosystems occurring in areas where water table depths are shallow, say less than 2 m, can reasonably be expected to require groundwater to satisfy most of its’ EWR. The degree of groundwater dependence is likely to reduce with water table depth, as the soil water reservoir has a greater capacity to meet plant water requirements.



Where available a comparison of ecological data (e.g. LAI, greenness, recruitment) with historical trends in groundwater quality and levels can provide the basis to draw a correlation between ecosystem function - groundwater dependence – water regimes. Transient ecosystem response observations can also assist in deriving an understanding of ecosystem resistance and resilience to changed water regimes.


T6 Surface water – groundwater hydraulics

Relative heights in water level between surface water and groundwater systems can indicate net direction of water flux. Losing surface water systems have water levels that are elevated in comparison to groundwater levels and are likely to receive water predominantly from surface water runoff. Gaining surface water systems have water levels that are lower than adjacent groundwater systems and are likely to rely on groundwater discharge. Many surface water systems may be losing systems during wet seasons and gaining during dry seasons.

Baseflow, Wetland


Groundwater discharge to surface water systems can cause distinct changes in the physical characteristics of surface water. For example, groundwater temperatures tend to be more constant than surface water temperatures and areas of groundwater discharge often provide critical habitat for reproductive cycles of aquatic organisms within surface water systems.

Baseflow, Wetland

T8 Water chemistry

Surface water chemistry is often modified predictably by groundwater discharge. For example, groundwater generally contains higher concentrations of major ions than surface water runoff. Abrupt increases in major ion chemistry concentration in surface water can often indicate groundwater discharge. Such increases in surface water major ion concentrations can also occur due to evaporative processes and care must be taken during interpretation to avoid confusion.

Baseflow, Wetland

T12 Conceptual model

Draw on knowledge from similar catchments, and on knowledge developed through addressing the data needs of tools T1 and T5 to develop a preliminary conceptual model of the role of groundwater in an ecosystem (can be a written description, sketch or flow diagram outlining the key features of dependence). If the level of study required to address the objective of a GDE study is deemed as basic, the conceptual model may be the most important outcome. For moderate to comprehensive studies, the conceptual model is continually developed throughout the investigations.


T13 Root depth & morphology

Experience can be drawn on in regard to known rooting depth of vegetation species to inform the conceptual model. Also, additional information can be derived from intrusive drilling investigations, where note is made of the occurrence of vegetative material in drill cuttings.


T14 Aquatic ecology

Biological species (possibly vegetation, macro-invertebrates or micro-organisms) that uniquely colonise areas of groundwater discharge can be identified and used as a bioindicator to define broader areas of groundwater discharge to surface water systems.

Baseflow, Wetland


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CASE STUDY #1 – CONCEPTUAL MODEL DEVELOPMENT

Conceptual models present a theoretical construct of the biophysical attributes of a system and the relationships between system components. As an example Figure CS.1 shows pre-development vs. post-development conditions within an hypothetical catchment.


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CASE STUDY #2 - IDENTIFYING POTENTIAL WETLAND GDES

There are several hundred perennial and ephemeral wetlands within the Lower Southeast of South Australia, although the extent of groundwater dependence of most of these is uncertain. A reconnaissance survey took place in 2004-05 to estimate the relative groundwater dependence of 37 wetlands based on the similarity of wetland and groundwater chemistry (refer Report 2 Field Studies). Of the various geochemical measurements that were made, radon and chloride appeared most useful for distinguishing between surface water and groundwater fed wetlands. A simple mass balance model was developed to determine volumes of surface water and groundwater inflow from radon and chloride concentrations. The ratio of groundwater inflow rate to surface water inflow rate and the ratio of groundwater inflow rate to wetland volume were used as measures of groundwater dependence. Groundwater dependence for the wetlands was then grouped as High, Moderate and Low, based on the values of these ratios (Figure CS.2).

Figure CS.2 Classification of wetlands into High, Moderate and Low groundwater dependence, based on ratios of groundwater and surface water inflow rates and the wetland water volume. Each circle represents an individual wetland. A value of one for the ratio of groundwater to surface water inflow indicates that these water sources contribute equally to water within the wetland. Higher values indicate a dominance of groundwater inflows.

5.5 Step 1.4; Setting ecological objectives

From the outset, any program of work undertaken to identify EWRs for GDEs, and ultimately EWPs, requires target setting and formalising hypotheses that describe groundwater and ecosystem behaviour in a form that can be tested by a monitoring program. The hypotheses are essentially conceptual models of ecosystem dependence on groundwater that have the objective of predicting, and then assessing, how ecosystems respond to changes in the natural water regime.

Defining ecological objectives involves describing the relationship between ecosystem function and (water) resource condition, and involves two components. Firstly, the form of groundwater

STEP 1.4

Setting ecological objectives

Purpose: Basing the assessment of EWRs on well defined ecological objectives allows the catchment manager to clearly define those aspects of an ecosystem that are to be protected and provide a basis from which to measure the success of water planning policy.


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dependence and how this might be affected by an altered water regime and, secondly, linking this outcome with resource management.

It is only possible to measure, manage (protect) and manipulate defined ecosystem variables, such as ecosystem extent, plant water use, recruitment and migration patterns. If appropriately selected, ecological objectives that are based on defined and measurable variables should be able to provide a basis for providing the level of protection afforded the broader ecosystem by water management policy and strategies, and so protect less tangible ecosystem characteristics such as cross-species reliance. Initially, broad goals may be defined to assist in describing the condition of the ecosystem in its target state.

In terms of setting ecological objectives it will often be easier and more appropriate to focus on direct relationships between ecosystems and groundwater. Indicators of ecosystem response to groundwater management will be more informative in the case of direct relationships. Most importantly, there is a feedback loop between this step and Step 2.4 (see Section 6 of this Framework and Figure 4.1).

Identifying ecological objectives essentially involves setting environmental targets that represent the level of biodiversity (health, numbers, regeneration etc.) to be achieved through water policy and management strategies. The objectives must be accompanied by performance indicators that will assist in informing those involved in resource management whether or not the overall objectives of water and ecosystem management are being achieved. An important consideration for any environmental monitoring and evaluation program that addresses the water needs of GDEs is the identification of those monitoring activities that have direct application in achieving desired policy or management outcomes, thereby ensuring available resources (both human and financial) are focused on monitoring activities that provide the most concise and relevant data (Howe et al, 2006).

Table 5.4 presents the two primary tools for setting ecological objectives. The use of other tools in the toolbox can be implicit in using the tools identified in the table.

Table 5.4 Tools for setting ecological objectives

Code Tool Example methods


Observed ecophysiological data (e.g. leaf area index, greenness, recruitment, leaf water potential) can be compared against historical trends in groundwater quality and levels to define interrelationships between ecosystem function - groundwater dependence – water regimes. Transient ecosystem response observations can also assist in deriving an understanding of ecosystem resistance and resilience to changed water regimes. This tool can be used to initiate the setting of ecological objectives if the necessary data are available. However, most often T5 will provide the basis for testing conceptual eco-hydrological models (T12) via a formal monitoring and evaluation feedback loop (see Figure 4.1). The entire toolbox can provide the means of observing ecosystem response to change, depending on the form of reliance on groundwater, budgets and timeframes.


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Table 5.4 Tools for setting ecological objectives (cont.)

T12 Conceptual modeling

Draw on knowledge from similar catchments, as well as ecological/hydrological/hydrogeological experience to develop a preliminary conceptual model of how ecosystems might respond to altered hydrological (groundwater, as well as surface and soil water) conditions. This will expand upon the conceptual eco-hydrological model developed as part of Step 1.3. Ongoing monitoring and evaluation (see T5 for example indicators) will inform the adequacy of the model, and identify where changes are to be made. Conceptual eco-hydrological models can be a written description, sketch or flow diagram of the key ecosystem-groundwater interactions, but must also include:

• the objectives that ecosystem management must achieve;

• the environmental or habitat requirements of the objectives; and

• the role of groundwater (and other water sources) in providing environmental conditions and habitat requirements, which should include an analysis of obligate or facultative dependence on groundwater.

Investigations and data collection should be designed to test conceptual models and so provide the basis for refining ERFs and EWRs.

The initial purpose of developing conceptual (eco-hydrological) models is to anticipate how the objectives for ecosystem condition respond to changes in groundwater availability and quality. They require information, firstly, on the direct ecosystem-groundwater relationships and, secondly, on the role of the species in energetic and nutrient pathways, and in physical habitat provision (i.e. the indirect ecosystem-groundwater relationships).

Few ecosystems are understood in sufficient detail for conceptual eco-hydrological models to be developed with certainty. Rather, they are a network of hypotheses and assumptions, some of which may be based on data source from the ecosystem in question but many of which will be based on general ecological principles. Setting of ecological objectives requires that these hypotheses and assumptions are presented in a form that is measurable and testable so that they can be refined on the basis of ongoing monitoring and evaluation programs.

Once the water required to achieve ecological objectives has ben established it is possible to identify whether there is water in the system that is surplus to environmental requirements and may be made available for other uses. The significance of surplus water is not often considered in ecological benchmarking, but may be very important in the overall water management framework. Ecological objectives are often set lower than the condition of an ecosystem under natural conditions, eg. an ecological objective may be to maintain viable species populations within a landscape, and less water may be needed to achieve this then would occur if population sizes were to remain as they were under natural conditions. Surplus water may:

• result from spasmodic events where water is very abundant and there is an excess not required to achieve ecological objectives as they are defined;

• support ecological processes that are not addressed by ecological objectives, and so are not considered important; and

• support ecosystem functions that are not well understood but may be important in meeting defined ecological objectives.


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In the last case, lack of information/data at the time of setting ecological objectives may cause problems in achieving ecological objectives in the future, which highlights the importance of formal monitoring and evaluation programs.

CASE STUDY #3 – DEVELOPMENT OF ECOLOGICAL OBJECTIVES FOR GDEs

A properly formulated water management plan, that addresses the EWRs of various ecosystem types, including GDEs, requires a clear definition of the desirable ecological outcomes that are to arise from plan implementation. Conceptual models will describe key ecosystem attributes that are maintained by the different components of a natural water regime, and form the basis for defining ecological objectives. Monitoring programs can then be implemented to assess the success of water management policy in meeting ecological objectives, and / or the adequacy of the conceptual models in describing ecosystem response to altered water regimes.

Some fundamental components of the Daly River, which is a baseflow fed stream in the Northern Territory, have been described by conceptual models developed by Erskine et al (2003) and refined through intensive field data collection and analysis.

Conservation policy identifies the preservation of the Pig-nosed Turtle (Carettochelys insculpta) population as an ecosystem management goal. The turtle (Plate CS.3) is of significant international conservation interest because it is the sole remaining member of a once wide-spread Family and because the best Australian populations are found on the Daly River. The Daly River also supports eight of the nine freshwater turtle species of the Northern Territory, and protecting the Pig-nosed Turtle will also likely conserve a number of these other species because they share common habitat requirements.

Groundwater baseflow to the Daly River influences in-stream water temperature and chemistry, both of which are important habitat requirements of the turtle. The conceptual eco-hydrological model for the turtle describes the species aquatic habitat requirements, and documents: (i) the role of water temperature in gender determination; (ii) requirements for clean sand banks, adjacent to water, for nesting; (iii) the extent and distribution of nesting sites; (iv) coincident hydrological and climatic triggers for hatching; (v) requirements for water depth to allow passage in shallow reaches; and (vi) the role of the aquatic plant Vallisneria nana as an important food source.

The water-related conditions that contribute to these habitat requirements (ecological objectives) were then explored using hydrological and hydraulic models, and ecological survey.

In terms of groundwater dependence and management, the Erskine et al (2003) study evaluated the role of groundwater in meeting ecological objectives, particularly in relation to food supply, physical habitat, migration and breeding. It was possible to describe how seasonal and inter-annual cycles of stream discharge, energy, depth and velocity influence these features. Ecological objectives were identified to meet the broad management goals for the Pig-nosed Turtle population. Plate CS.3 Pig-nosed turtle (photo: John Cann)


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6 STEP 2; IDENTIFYING PROCESSES

6.1 Overview Figure 6.1 presents a summary of Step 2 of the Framework, which has the objective of identifying the various processes governing the interaction between GDEs and the various possible components of the “natural” water regime on which they depend (groundwater, as well as soil water and surface water). This section describes the tools available and methods that can be employed to identify and measure groundwater dependence (degree and form of) and so establish the water regime that is necessary to maintain the important ecological function of the GDEs under study.

Figure 6.1 Step 2 of the Framework, which identifies GDE water requirements, as well as assessing how water affecting activities might impact on ecological function.


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Step 1 of the Framework will have already established where the GDEs exist within the landscape, as well as whether they are terrestrial, stream baseflow or wetland ecosystems, and the important groundwater attributes that need to be considered when assessing the form of their dependence.

Step 2 is designed to move on from the important but preliminary (in terms of EWR determination) Step 1 assessment by establishing a detailed understanding of the way in which GDEs interact with groundwater as well as the other parts of the hydrological cycle and then, by means of threat and vulnerability assessments and an analysis of consequence and likelihood, determine the EWR of GDEs being studied. Threatening activities are those having the potential to impact on water availability for GDEs, vulnerability relates to degree of dependence, consequence equates the potential for loss of biodiversity / ecosystem services, and likelihood considers the risk that certain consequences will occur. More detail concerning each of these factors are provided below.

Apart from mapping tools (T1) and system response to change (T5), most of the tools that make up the GDE toolbox have not been widely used to establish ecosystem water requirements for the purpose of water allocation planning. Typically, the tools have been developed and used by research organisations to develop an understanding of ecosystem interactions with different forms of water and the processes involved in ecosystem groundwater dependence. However, the opportunity now exists to apply the tools for water resource planning and management.

In terms of the earlier frameworks / methodology, this Step of the GDE Framework addresses:

• form of groundwater dependence (Clifton and Evans, 2001; and Howe et al., 2006);

• determination of EWRs (Clifton and Evans, 2001; Howe et al., 2006, and Eamus et al., 2006);

• impact of altered water regimes on GDE function (Clifton and Evans, 2001; Howe et al., 2006).

Sections 6.2 and 6.3 present tools and methods that can be employed to develop an understanding of groundwater dependency and define EWRs for terrestrial, wetland and stream baseflow GDEs, respectively.

6.2 Step 2.1; Establish relationships between GDEs & their hydrological environment

Terrestrial GDEs Qualitative assessment of the impacts of altered water regimes on terrestrial GDEs, such as water table drawdown and increasing groundwater salinity, can best be assessed by empirical observations, both from the site in question and from other sites that have similar biophysical settings. This approach is essentially encapsulated with T5 (system response to change). In the absence of observation data, however, quantitative assessment of vegetation dependence on

STEP 2.1

Establish relationships between GDEs & their hydrological environment

Purpose: To fully understand the contribution groundwater makes toward meeting terrestrial GDE water requirements it is necessary to identify at a temporal and spatial scale all sources of water accessed by terrestrial GDEs.


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groundwater will require field investigation, some being quite labour and cost intensive, and predictive analysis involving numerical and analytical models.

Of the four groundwater attributes, terrestrial GDEs will tend to be primarily reliant on head (or groundwater level/depth to capillary fringe). For these types of GDEs, access to groundwater means maintenance of water table levels at depths that can be accessed by plant roots. However, changes in groundwater quality (typically salinity, but in some instances toxic chemicals and nutrients) may also be limiting factors to normal ecological function. In order to enable adequate description of the groundwater regime necessary for particular GDEs in particular locations it is necessary to develop a detailed understanding of the sources, timing and ranges in the quality of water used by vegetation, in addition to where in the landscape GDEs occur.

Perennial terrestrial vegetation often require access to other sources of water in environments where there is insufficient intra-annual or inter-annual rainfall to replenish the soil water reservoir as it is depleted by evapotranspiration processes. In many instances, this other source of water is groundwater. Some tree species that grow in arid environments can tolerate levels of water-stress that would not be tolerated by temperate tree species, even so, access to groundwater may be necessary during extended dry periods.

For the purpose of defining groundwater dependency, if vegetation utilises groundwater at some stage of its life-cycle, it is considered that groundwater dependence exists. However, access to groundwater could potentially be replaced by an increased soil water reservoir due to a falling water table. Declining groundwater levels can potentially benefit vegetation growth, by allowing a more extensive rooting zone and increasing the soil volume available for soil water storage (Jackson et al., 2000). However, there are few examples of declining groundwater levels producing benefits to vegetation condition (Naumburg et al., 2005).

Groundwater dependent vegetation may require access to groundwater continuously, seasonally (toward the end of the dry season) or episodically (during drought conditions). Some riparian vegetation may rely solely on groundwater (Snyder and Williams, 2000). However, terrestrial vegetation will preferentially extract water from areas where the combination of hydraulic conductivity, soil moisture content and root density requires the least amount of energy (Adiku et al., 2000; Naumburg et al., 2005), and it can be expected that terrestrial vegetation will use shallow soil water before switching to soil water deeper in the profile, or groundwater as the soil water reservoir becomes depleted.

Groundwater dependent vegetation may rely on groundwater levels remaining within a certain range over specific periods of time. For example, once the soil water store is depleted toward the end of prolonged dry periods (either seasonally or episodically) vegetation may require groundwater levels to remain within (say) four metres of the ground surface until new season rains re-wet the soil profile.

Alternatively terrestrial vegetation may not tolerate high groundwater levels for extended periods of time (e.g. Black Box in northern Victoria). This will depend on the flood tolerance of the vegetation species and whether water inundation occurs during periods of active growth (high impact) or dormancy (low impact). However, in natural systems high groundwater levels generally coincide with periods of active growth (Naumburg et al., 2005).

Some groundwater dependent vegetation can adapt to changes in groundwater level by extending root networks to greater depths (maximum rooting depths range from 0.3 to 68 m for different plant species; Canadell et al., 1996). However, many species could be expected to be


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sensitive to the rate of water table decline. Banksias growing over the Gnangara (groundwater) mound in Western Australia were found to tolerate declines in groundwater level, so long as they occurred at a rate of less than half a metre per year (Groom et al., 2000). Roots of Eucalyptus seedlings have been measured to elongate at rates of 5 mm/day (Misra, 1997).

Vegetation requiring access to groundwater for maintenance of normal ecological function may be sensitive to changes in groundwater quality. Salts that have built up in the unsaturated root zone of native vegetation typically remobilise and migrate down to the water table after native vegetation is replaced with lower water use vegetation. This can cause the salinity of groundwater to increase to levels that cannot be tolerated by remnant vegetation that relies to some extent on groundwater. Mensforth et al. (1994), and Holland et al. (2006) present discussion on the effects of groundwater salinity on terrestrial and riparian vegetation health, with the latter presenting the results of various floodplain inundation models on soil salinisation and vegetation health.

Terrestrial GDEs may require access to groundwater continuously, seasonally or episodically (obligate GDEs). However some species that depend on groundwater may also inhabit other environments where groundwater is not available (facultative GDEs), i.e. their water requirements can be satisfied by other water sources. In such cases, reduced groundwater availability may result in localised stress but will not necessarily cause local extinction as the affected species can recolonise and function in the “new” water regime.

Table 6.1 presents a summary of the tools that can assist in establishing the relationships between terrestrial GDEs and groundwater.

Determining the sources of water utilised by potentially groundwater dependent vegetation will:

1. confirm whether or not terrestrial ecosystems depend on groundwater; and, if so

2. determine whether these ecosystems are wholly or partially dependent on access to groundwater.

Once an adequate level of understanding is achieved regarding the relationship between GDEs and groundwater (constrained by scope, available budgets and resources), the next critical steps toward deriving EWRs can be taken, i.e. an analysis of:

• threatening processes that may impact on GDE water availability; and

• GDE water requirements.


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Table 6.1 Tools to assist in establishing relationships between terrestrial GDEs & groundwater

Code Tool Example methods T2 Water balance • Preliminary to detailed level of assessment required;

• groundwater use can be determined from water balance measurements and / or calculations. Using this approach, it is assumed that plant water use in excess of what could be expected to occur within the soil water reservoir is sourced from groundwater;

• a preliminary water balance can be based on knowledge / estimates of rainfall, potential evapotranspiration, depth to water and soil type;

• water balances can be progressively refined and extended spatially and temporally with the availability of new data (i.e. transpiration rates, soil moisture content, PAWC, time-series data, remote sensing surface energy balance and evaporation);

• in the absence of long-term vegetation health information, the regime of groundwater dependence can initially be tested by formulating a water balance based on rainfall records, estimating groundwater recharge, knowledge of plant water use, soil type and depth to groundwater (see Case Study #4);

• PAW can be compared to seasonal plant water demand to assess whether the soil water reservoir is sufficient to sustain plant water requirements for periods of historical rainfall (or recharge) records, giving an indication of the frequency and timing of access to groundwater required by terrestrial vegetation for maintenance of species / habitat persistence.


• Detailed level of assessment required;

• pre-dawn leaf water potential and soil water potential, combined with stable isotopes of water (T4) studies can indicate the primary sources of plant water, e.g. different depths in the soil profile or from the water table;

• measurement of pre-dawn leaf water potential (Ψlf) provides a basis for determining the depth from which plants extract water, when combined with soil matric potential data;

• isolated measurements will indicate the depths in the soil profile from which plant water uptake occurs at unique points in time;

• if only one sampling event is intended, it should be timed when vegetation is most likely to be accessing groundwater, i.e. following prolonged dry periods when the soil water store is likely to be depleted; however

• in terms of assessing the nature of vegetation groundwater dependence (timing, degree, water partitioning), sampling events would preferably be conducted following wet and dry seasons, over a series of years (if funding allows), as this will enable boundaries to be placed around soil water and groundwater regimes (water potential, water table depths etc.) within which the GDEs operate;

• water balances can be progressively tested and refined by field measurements and incorporating more accurate information, for example the timing of groundwater use can be confirmed / refuted using pre-dawn leaf water potential.


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Table 6.1 Tools to assist in establishing relationships between terrestrial GDEs & groundwater (cont.)

Code Tool Example methods T4 Stable isotopes • Measurement of the stable isotopes of xylem water (δ2H and / or δ18O) indicates the δ2H and δ18O signature of the source(s) of

water used by plants for transpiration. Comparison of xylem water δ2H and δ18O signatures to those of the potential sources of water for plant transpiration (i.e. rainfall, soil water, groundwater) can indicate the predominant source(s) of water utilised by plants;

• δ2H and δ18O signatures of the potential sources of water for plant transpiration have to be distinctly different for the technique to be useful.;

• δ2H and δ18O of xylem and soil water are often sampled in tandem with leaf water and soil matric potential measurements because very little additional effort is required for the complementary data;

• as with the pre-dawn leaf water potential technique for identifying the sources of water used by vegetation for transpiration, stable isotopes of water will (at best) indicate the location in the soil profile from which plants extract water at a single point in time and, as such, multiple measurements would be required to indicate the seasonality and inter-annual variability of groundwater use;

• water balances can be progressively tested and refined by field measurements and incorporating more accurate information, for example the timing of groundwater use can be confirmed / refuted using isotope studies.


• long-term observations of vegetation condition in response to climate and / or changes in groundwater depth and quality (due to natural variability and / or anthropogenic factors) can be used to indicate those plants accessing groundwater in comparison to those that rely on soil water to satisfy their water requirements;

• further analysis of long-term trends can be used to establish vegetation environmental response requirements (EWRs);

• long-term observation of changes in vegetation condition in response to seasonal and episodic changes in groundwater level or quality (due, for example to climate variability and land-use change) may provide an indication of when and for what duration vegetation accesses groundwater;

• where fluctuations in groundwater levels are consistent with those under natural conditions, changes in groundwater salinity can be compared to changes in vegetation condition to assess groundwater salinity regimes that can be tolerated by terrestrial vegetation (Bell, 1999 lists groundwater salinities that a selection of Australian vegetation is reported to tolerate);

• where groundwater regimes are altered from natural conditions changes in groundwater salinity are likely to be a secondary factor affecting groundwater dependent vegetation condition.

T9 Introduced tracers • not widely used, but a small number of studies (e.g. Haase et al., 1996) have tagged groundwater with artificial tracers to assess whether terrestrial vegetation has access to soil water or groundwater;

• similar in approach to stable isotopes.


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Table 6.1 Tools to assist in establishing relationships between terrestrial GDEs & groundwater (cont.)

Code Tool Example methods T10 Plant water use

modeling • plant water use models can incorporate soil physical properties (eg. Cook and O’Grady, 2006)

• the models can be utilised to test how depleted soil water reservoirs or declining water tables impact on plant ecophysiological responses;

• typically requires both a detailed knowledge of soil physical properties and plant physiology to be useful, and will often be limited by available data.

T11 Groundwater modeling

• numerical modeling can be used to explore the availability of groundwater and / or soil water to vegetation communities in response to management actions;

• note that groundwater availability for plant uptake does not necessarily signify groundwater use as soil water may form the preferred source of plant water depending on soil water potentials;

• groundwater modelling cannot definitively indicate groundwater use unless it is linked to one or more of the following tools – T2, T3, T4, T5 and T13;

• groundwater models can be integrated with plant water use models (T10) to test under what climatic / land-use conditions terrestrial vegetation require access to groundwater for long-term survival, i.e. when the soil water store is insufficient to satisfy evaporative demand.


• the benefits arising form conceptual model development rely entirely on the quality of the data and information on which the model is based;

• may require the input of ecologists, hydrologists, hydrogeologists, hydrogeochemists and ecophysiologists.


• knowledge / measurement of vegetation root depth and the morphology of root systems in comparison to depth to water can provide a strong indication of whether vegetation sources water purely from the vadose (soil water) zone or from a combination of the vadose and saturated zones;

• this technique is based on the assumption that if plant roots extend to the (variably) saturated zone (including the capillary fringe), access to groundwater is required to meet transpiration demand during some phase of the climatic / groundwater regime;

• rate of root growth and maximum rooting depth data / information is required to determine the rate of groundwater level decline that groundwater dependent vegetation can tolerate (eg. Froend and Drake, 2006);

• root growth and distribution data information is available in current literature for some plants (refer Canadell et al, 1996 for maximum rooting depth of various plants growing in Australia that are reported in the literature), but may be limited by hydrogeological and geological factors (e.g. soil physical properties, and water table depth);


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CASE STUDY #4 – WATER BALANCE MODELING

Typically, groundwater only forms one component of terrestrial GDE water requirements. This is especially the case in temperate and tropical areas where rainfall is seasonal and there is an opportunity for the soil water store to be replenished annually and provide a source of water during part or all of the dry season. It can be expected that as the soil water store is depleted, terrestrial GDEs will become increasingly dependent on groundwater.

A water balance model was utilised in Queensland’s Pioneer Valley to assess whether the soil water store is sufficient to meet plant water requirements (Howe et al., 2006). The water balance takes the form of:

DSWS QQPS −−=∆

where ∆S is the change in soil moisture storage, QWS is the wet season water use, QDS is the dry season water use, P is the wet season precipitation. Dry season precipitation was assumed to be negligible, and the water use terms include soil evaporation and understorey transpiration. The magnitude of the soil moisture storage (S) is constrained according to:

PAWCzS r ×≤≤0

where zr is the maximum rooting depth of the vegetation, and PAWC is the plant available water capacity of the soil (mm/m).

In very simple terms these types of water balances can be conducted assuming average annual rates of precipitation. However, a more robust transient approach was adopted for the Pioneer Valley water balance whereby historical rainfall records were utilized to assess the risk of plant water shortage in any one year (Figure CS.4).

Assumptions underlying the analysis included: (i) soil water is drawn on in preference to groundwater; (ii) low PAWC during dry seasons will trigger groundwater use; and (iii) maximum rooting depths are equal to water table depth.

Figure CS.4 Modeled risk of GDE impact based on plant available water (mm; PAWC x depth to water table). The results essentially describe an environmental response function for Pioneer Valley terrestrial GDEs, and indicate that a high risk (more than 4 in every 10 years) of plant water shortage will occur where PAWC is less than 300 mm (equivalent to a PAWC of 75 mm/m and a 4 m water table depth).


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CASE STUDY #5 – USE OF WATER POTENTIALS AND STABLE ISOTOPES IN ASSESSING TERRESTRIAL VEGETATION DEPENDENCE ON GROUNDWATER

It is recognised that plant communities often access more than one water source to meet their water requirements, eg. recent rainfall, soil water and groundwater, and that this water partitioning is important in determining community and habitat structure. Understanding plant physiological adaptations to groundwater use is important in understanding the response of dependent vegetation to altered water regimes.

Studies conducted in the Ti-Tree Basin, Northern Territory, detailed in Report 2 Field Studies, had, among others, the aim of identifying tree species that are dependent on groundwater. Various methods were utilised to assist in this determination, eg. measuring tree water use with sapflow loggers, measuring diurnal patterns of leaf water potential, measuring soil matrix potentials and measuring the stable isotope of 18O composition of soil water, plant water and groundwater.

Figure CS.5 presents plots of leaf water potentials for different tree species against soil matric potentials (water table depth is approximately 6 m), and 18O composition of plant water against that of soil water and groundwater.

Depth of water abstraction can be obtained by comparing LWP and 18O composition of plant water against soil water potential and 180 composition .

Figure CS.5 Water potential and isotope data indicate E. victrix and C. opaca are groundwater dependent (water potentials suggest these species access water from the capillary fringe and plant water 18O composition suggests water uptake occurs from between the depths of 4.5 and 6 m).

Leaf water potential data for A. aneura are not conclusive as to depth of water uptake. However, plant water 18O composition strongly indicates this species draws water from the top 2 m of the soil profile, and that the species is not groundwater dependent.

Stream baseflow and wetland GDEs There are three main facets of river and wetland ecosystems that could potentially require access to groundwater at some point in time in their respective hydrological cycles to maintain ecosystem function:

1. the surface water environment;


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2. subsurface refuges; and

3. vegetation fringing river or wetland ecosystems.

Some important questions to be addressed in the assessment of environmental flows for potential stream baseflow and wetland GDEs include:

• does groundwater maintain low flows and water quality in streams and wetlands, either seasonally or across years?;

• does groundwater provide constant temperature habitat for aquatic biota, eg. for breeding purposes?; and

• does groundwater provide essential nutrients for ecosystem function?.

Generally, the dependence on groundwater of river and wetland ecological processes is poorly understood. Although the assessment of environmental flow requirements for Australian riverine ecosystems is a well established process in Australia, Boulton and Hancock (2006) observe that there has typically been little recognition of the contribution (degree and timing) of groundwater to the maintenance of in-stream ecosystems. This is probably more so the case for wetland ecosystems.

As the approach to environmental flows policy for Australian rivers and streams is focused primarily on the management of surface water components of flow, whilst not explicitly recognised in the environmental flow assessment process groundwater is implicitly acknowledged in the overall aquatic EWR. However, this does not mean that potential groundwater affecting activities (eg. groundwater pumping and land clearance) are addressed in environmental flow management frameworks.

River baseflow and wetland GDEs will require specific frequencies and durations of access to groundwater, with the key groundwater attributes for these types of GDEs typically being flux and quality. In some cases head / pressure may be important attributes, eg. in the case of the Great Artesian Basin springs (pressure dependent) and ephemeral systems (head dependent via access to shallow water tables). Access to groundwater means the maintenance of water table levels, groundwater pressures or hydraulic gradients at specific times and durations such that: (i) groundwater flux / discharge are sufficient to sustain aquatic biota (e.g. flora / fauna dependent on the surface expression of groundwater); (ii) water tables remain shallow enough to sustain subsurface refuges; or (iii) water tables are maintained at depths that can be accessed by fringing (riparian) vegetation.

For the purpose of defining groundwater dependency, it is often assumed that if stream baseflow or wetland systems have a component of groundwater within their “natural” water regime groundwater is required for maintaining some aspect of ecosystem function, distribution or structure. However, access to groundwater could potentially be replaced by:

• An increased soil water reservoir due to a falling water table, which may accommodate the water needs of some riparian and fringing aquatic vegetation and hyporheic ecosystems, but possibly not aquatic ecosystems dependent on open water. However, as indicated for terrestrial vegetation, there are few examples of declining groundwater levels producing benefits to vegetation condition (Naumburg et al., 2005).


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• Stream flow losses along riparian zones of supplemented streams. Howe et al. (2006) identified stream flow losses likely supported stands of Corymbia dallachiana along a Queensland Central Coast stream that was supplemented for irrigation supplies.

Obligate groundwater dependent river baseflow or wetland ecosystems may require access to groundwater continuously, seasonally or episodically. However some species that depend on groundwater in river baseflow and wetland ecosystems, may also inhabit other environments where groundwater is not available (facultative GDEs), i.e. their water requirements can be satisfied by other water sources. In such cases, reduced groundwater availability may result in localised stress but will not cause local extinction as the affected species can recolonise and function in a “new” or “altered” water regime.

Some obligate groundwater dependent riparian vegetation may have the ability to adapt to small decreases in groundwater levels by extending roots. However, obligate aquatic biota may be less capable of adapting to reduced groundwater access, eg. where groundwater sustains permanent pools during dry periods, or where shallow groundwater provides dry season refuges for some aquatic species. Similarly, biota existing within the hyporheic zone beneath ephemeral streams may be adversely impacted by declining water tables.

There may be instances where wetland GDEs, in particular, do not tolerate prolonged inundation (giving rise to anoxic conditions) or altered groundwater to rainfall ratios (which may impact wetland water chemistry).

River and wetland ecosystems depend on specific ranges in solute (e.g. salinity, nutrients) concentrations to provide suitable habitat for the longevity of aquatic biota. In many river and wetland ecosystems, water quality is regulated by groundwater influx. Altered groundwater salinity, the introduction of harmful solutes or reductions in the availability of essential nutrients will also critically affect the function of river baseflow and wetland ecosystems. As such, to adequately describe the groundwater regime required by river baseflow and wetland GDEs, it will be necessary to develop a detailed understanding of the sources, timing and ranges of water quality that river baseflow and wetland GDEs are exposed to, eg.:

• Land use change can cause groundwater salinity to increase to levels that cannot be tolerated by river baseflow or wetland ecosystems (Nielsen et al., 2003).

• In areas where groundwater regimes are altered from natural conditions, changes in groundwater quality is likely to be a secondary factor affecting groundwater dependent river/wetland ecosystem condition.

• In regions where fluctuations in groundwater levels are consistent with those under natural conditions, changes in groundwater quality can be compared to changes in river/wetland ecosystem condition to determine groundwater quality regimes that are desirable or tolerable for aquatic biota.

• Even if groundwater is a minor component of water contributing to stream baseflow and wetland ecosystems, it may supply essential solutes to sustain ecosystem function. Whilst access to additional water may not be required, the nutrients delivered to river baseflow and wetland ecosystems by groundwater may be essential for maintaining ecosystem condition. Decreases in the delivery of nutrients to river baseflow or wetlands ecosystems, as a result of decreased groundwater discharge, may limit the growth / reproduction of aquatic biota. Conversely, increased nutrient delivery as a result of


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inefficient application of fertilisers may enhance the growth of specific species, leading to an imbalance in the receiving ecosystem, potentially causing eutrophication (the process whereby excess nutrients are delivered to surface water environments causing enhanced plant growth, reduced dissolved oxygen in the water when dead plant material decomposes and potential death of other organisms as a result.

• Inefficient application of herbicides / pesticides or chemical spills can result in harmful solutes being delivered to surface waterways via groundwater discharge, potentially endangering GDE condition.

• Groundwater discharge to surface water environments can provide areas of relatively stable temperature that are often inhabited by aquatic biota that tolerate narrow ranges of temperature. Reduced groundwater discharge in these instances will decrease / remove habitat for specific aquatic biota, which is likely to put pressure on other species higher in the food web. As examples, some species of fish preferentially lay eggs in areas of groundwater discharge because it prevents the eggs from freezing during winter (Vaccaro and Maloy, 2006), and springs along some reaches of the Northern Territory’s Daly River create environments of relatively stable temperature, creating favourable nesting sites for the endangered pig-face turtle (Erskine et al, 2003).

A literature search can assist in defining ranges of solute concentrations that key aquatic biota can tolerate. For example, Appendix A.3 lists the salinity tolerance of aquatic biota from the Barwon River under laboratory conditions (Kefford et al., 2003). Similar studies have been undertaken on fish species (Ryan and Davies, 1996; Clunie et al., 2002; James et al., 2003), however, aquatic biota appear to be more vulnerable than fish to increases in salinity (Kefford et al. 2004). Appendix A.4 lists the salt tolerance of fish in the Murray-Darling Basin during different lifecycle stages.

Table 6.2 presents a summary of the tools that can assist in establishing the relationships between groundwater, and stream baseflow and wetland GDEs. Of particular importance regarding the use of the tools is the level of monitoring already undertaken and the status of monitoring infrastructure already available in areas of interest. The manner and order in which the tools presented in Table 6.2 are employed will depend on the datasets available at the time of individual studies.

Determining the sources of water utilised by potentially groundwater dependent vegetation will:

1. confirm whether or not aquatic and/or riparian ecosystems depend on groundwater; and, if so

2. determine whether these ecosystems are wholly or partially dependent on access to groundwater.

Once an adequate level of understanding is achieved regarding the relationship between wetland and baseflow GDEs and groundwater (constrained by scope, available budgets and resources), the next critical steps toward deriving EWRs can be taken, i.e. an analysis of:

• threatening processes that may impact on GDE water availability; and

• GDE water requirements.


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Table 6.2 Tools to assist in establishing relationships between stream baseflow and wetland GDEs

Code Tool Example methods T2 Water balance Riparian GDEs

• groundwater use can be determined from water balance measurements and / or calculations (refer to terrestrial GDEs for more detail, Table 6.1)

In-stream and hyporheic GDEs • major ion chemistry (T8) can potentially be used to determine the proportion of groundwater contained in surface water systems by

employing a mass balance approach

• calculations need to consider surface water storage, evaporative losses, surface water inflows / outflows and rainfall, with groundwater discharge being the balancing term (may indicate groundwater contribution to stream flow, or surface water contribution to groundwater

• more detailed and accurate water balances can be developed where flux terms are constrained by field measurements/modeling, requiring output from tools T4, T6, T8, T9 and T11


Riparian GDEs • pre-dawn leaf water potential and soil water potential (combined with stable isotopes of water; T4) studies can indicate the primary

sources of plant water (refer to terrestrial GDEs for more detail, Table 6.1)

• one off field studies should be timed to occur toward the end of dry seasons or drought periods, but to fully consider groundwater dependence it is recommended that studies encompass all seasons

T4 Stable isotopes Riparian GDEs • stable isotopes of water (combined with pre-dawn leaf water potential and soil water potential; T3) studies can indicate the primary

sources of plant water (refer to terrestrial GDEs for more detail, Table 6.1)



General • long-term observations of groundwater levels and stream gauge (T6), water chemistry and physical properties (T7 and T8) and

aquatic biota condition (T14) in response to climate and / or changes in groundwater depth and quality (due to natural variability and / or anthropogenic factors) can be used to indicate river and wetland ecosystem interaction / reliance on groundwater

Riparian GDEs • long-term observations of vegetation condition in response to climate and / or changes in groundwater depth and quality (due to

natural variability and / or anthropogenic factors) can be used to indicate those plants accessing groundwater in comparison to those that rely on soil water to satisfy their water requirements (refer to terrestrial GDEs for more detail, Table 6.1)


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Table 6.2 Tools to assist in establishing relationships between stream baseflow and wetland GDEs (cont.)

Code Tool Example methods T5 System response to

change In-stream and hyporheic GDEs • long-term monitoring of surface water and groundwater levels can indicate reaches of streams or wetlands where the potential for

groundwater discharge exists

• historic baseflow separation of stream gauge data can be used to generate baseflow indices to estimate the proportion and timing of groundwater discharge making up stream flow (T6), and provide information to assist in the assessment of transient ecological data

T6 Surface water – groundwater hydraulics

Riparian GDEs • surface water discharge from streams and wetlands to groundwater will occur where groundwater levels in the water table aquifer

adjacent these water bodies are lower than stream or wetland gauge In-stream and hyporheic GDEs • groundwater discharge to streams and wetlands will occur where groundwater levels in the water table aquifer adjacent these

water bodies is higher than stream or wetland gauge

• the more comprehensive the surface water and groundwater monitoring infrastructure the better the quantification of surface water – groundwater interaction will be

• historic baseflow separation of stream gauge data can be used to generate baseflow indices to estimate the proportion and timing of groundwater discharge making up stream flow, as well as natural variability

• Darcy’s Law can be used to estimate the rate of discharge between groundwater and surface water systems (Q=KiA - where Q = discharge, often expressed as mm; i = hydraulic gradient; and A = area over which discharge occurs)

• may underestimate discharge to the hyporheic zone, particularly in low gradient hydraulic environments



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Code Tool Example methods T7 Physical properties

of water In-stream and hyporheic GDEs • potential influxes of groundwater to surface water systems can be indicated by abrupt changes in physical parameters along the

length of river or at different locations in a wetland

• useful for narrowing down areas for more detailed investigation (e.g. aquatic ecosystem studies) because it does not necessarily require installation of monitoring infrastructure or expensive laboratory analysis

• although all tools grouped here are not physical parameters of water (i.e. dissolved oxygen, pH, total dissolved solids[1], as opposed to temperature and electrical conductivity), they can be monitored and results viewed and interpreted instantaneously using a hand-held meter

• run-of-river temperature surveys along flowing stream reaches, in particular, can provide an indication (snap-shot in time) of where groundwater discharge takes place to the surface system

• time series run-of-river temperature data combined with climatic records can provide information concerning the transient nature of groundwater discharge to surface water systems


• limitations: - physical properties of groundwater may only persist for short times in the surface water environment (e.g. temperatures may rapidly equilibrate with surface conditions) - groundwater discharge to surface water systems cannot easily be quantified and surface water ecosystem dependence on groundwater contribution can only be inferred

1 Total Dissolved Solids (TDS) is not measured in the field using a hand-held meter, however, electrical conductivity (EC) multiplied by some conversion factor, F (e.g. TDS = EC × F, where F ranges between 0.5 and 1), is often used as a surrogate for TDS. Laboratory analysed TDS (by ion balance) should be used for calculation of groundwater discharge to surface water ecosystems.


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Code Tool Example methods T8 Water chemistry In-stream and hyporheic GDEs

• chemical properties that are distinctly different between groundwater systems, and the surface water systems they potentially discharge to, can be used to identify the occurrence of groundwater discharge to surface water environments;

• run-of-river salinity / radon / major ion (etc.) surveys along flowing stream reaches and wetlands, in particular, can provide an indication (snap-shot in time) of where groundwater discharge takes place to the surface system;

• time series run-of-river salinity / radon / major ion (etc.) data combined with climatic records can provide information concerning the transient nature of groundwater discharge to surface water systems;

• naturally occurring radioactive (e.g. 222Rn) or radiogenic (e.g. 87Sr/86Sr) tracers can also be used to identify the presence of groundwater in the hyporheic zone, streams and wetlands, depending on differences in groundwater sources, note: other data requirements (e.g. surface water discharge, 222Rn activity of groundwater) and expert analysis is required;

• quantitative interpretation of 222Rn data is still in its infancy (wetlands: Report 2; rivers: Pritchard, 2005) and is semi-quantitative.

• enhanced surface water and groundwater mixing can occur within the hyporheic zone - differences in the major ion concentrations of surface and subsurface waters can indicate sources of water to the hyporheic zone, although care should be taken as evapo-concentration of major ions in surface water environments can make interpretation of hyporheic zone water sources ambiguous - the oxidation-reduction state of the hyporheic zone enhances biogeochemical reactions involving most major ion species, therefore interpretation of hyporheic zone source waters can be complex - the different potential hyporheic zone source waters may have distinctive stable isotopes of water signatures (caused by evaporative processes).



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Code Tool Example methods T9 Introduced tracers In-stream and hyporheic GDEs

• introducing tracers to the groundwater system and analysing surface water samples down gradient of the point of introduction can provide strong evidence of groundwater – surface water interaction;

• suitable tracers need to have a very low level of detection to overcome influences of dilution and dispersion;

• associated field and analytical work is not trivial and can be ‘hit-and-miss’ in terms of placement of monitoring wells, as well as being time-consuming and laborious

• controlled introduced tracer experiments to surface water systems can be used to determine groundwater discharge by monitoring changes in tracer concentration, surface water inflows and outflows over specific time periods (e.g. Lamontagne et al., 2003)

• limitations: - by injecting a tracer to the subsurface (or surface) environment, the natural hydraulics of the system are altered, which may induce groundwater discharge to the surface water system - in low hydraulic conductivity or low hydraulic gradient environments a tracer injected to groundwater may take a long time to appear in the surface water environment - dispersion may impact the time over which tracer is detected - persistence and reactivity of the introduced tracer in the surface water and groundwater ecosystem need to be considered in terms of the usefulness of the tracer over appropriate time-scales, any potential harmful or objectionable (odour or discolouration) consequences associated with its introduction to the surface water or groundwater environment also need to be considered - tracers injected into groundwater cannot be used to determine the dependence of the surface water ecosystem on groundwater

T10 Plant water use modeling

Riparian GDEs • plant water use models can be utilised to test how depleted soil water reservoirs or declining water tables impact on plant

ecophysiological responses (refer to terrestrial GDEs for more detail, Table 6.1), this may ne in response to both groundwater and surface water use


General • can be used to explore the availability of groundwater to river baseflow and wetland ecosystems prior to onset of threatening

activities, and the impact of threatening activities when they occur

• will not necessarily indicate obligate or facultative groundwater use, unless combined with other tools, eg. system response to change (T5) or analysis of aquatic ecology (T14)


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Code Tool Example methods T12 Conceptual

modeling Riparian GDEs • groundwater and surface water hydraulic studies can be utilised to develop a conceptual understanding of groundwater – surface

water interaction In-stream and hyporheic GDEs • simultaneous analysis of the stable isotopes of water with major ion chemistry (T8) of potential water sources of the hyporheic

zone can assist in development of a conceptual model of stream-aquifer interaction, aiding distinction between evaporative processes and mixing of different source waters


Riparian GDEs • knowledge / measurement of vegetation root depth and the morphology of root systems in comparison to depth to water can

provide a strong indication of plant water sources (refer to terrestrial GDEs for more detail, Table 6.1)


In-stream and hyporheic GDEs • identification of aquatic biota and ecosystem processes known to have obligate groundwater dependence rather than facultative

dependence will confirm GDE status

• the presence of obligate groundwater invertebrates (stygofauna) in the hyporheic zone can also provide conclusive evidence of groundwater – surface water interaction

• a developing science, with few tools available for identifying sources of water to subsurface refuges

• absence of known obligate species does not negate river or wetland dependence on groundwater


• does not require the installation of permanent monitoring infrastructure


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Figure CS.2 Elliot River Baseflow Index

0%

10%

20%

30%

40%

50%

60%

70%

80%

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Month (based on average from 1974 - 2004)

Bas

eflo

w In

dex

Dr May's Crossing - 137003A

Elliot - 137001B

CASE STUDY #6 – IDENTIFYING BASEFLOW CONTRIBUTION TO RIVERS

In many parts of Australia, where rainfall occurs seasonally, baseflow can form an important component of aquatic ecosystem environmental water requirements. This is particularly the case during dry times of the year when surface water runoff (quickflow) following rainfall events rarely occurs. Baseflow can be an important source of water for in-stream and hyporheic ecosystems, and may have a role in maintaining transient in-stream hydrochemical conditions that are important to ecosystems (see Case Study #3 for an example).

Comparison of potentiometric surface maps with river bed elevations indicate that all of the major rivers in Queensland’s Coastal Burnett area potentially gain groundwater from the shallowest coastal aquifer. The Elliott River has been shown to be an highly dependent GDE upstream of the limit of tidal influence during the dry season (SKM, 2005). Baseflow separation analysis clearly shows this, indicating that on average over the past 30 years groundwater contributed more than 50% of flow to the Elliott River for 5 months of the year (June to October), peaking in July when the contribution is up to 70% (Figure CS.6).

These average monthly results mask the fact that dependence on baseflow increases significantly during prolonged dry spells. During such periods, including periods of no flow, baseflow will serve a key role in maintaining saturated streambed sediments and permanent pools, and the biota that require these refuges during dry periods.

Available evidence suggests river extractions and groundwater pumping are impacting on low flow conditions in the Elliott River.

Figure CS.6 Elliot River baseflow index, showing the importance of baseflow for maintenance of stream flows (on average) between June and October every year.


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CASE STUDY #7 – USE OF TRACERS IN ASSESSING GROUNDWATER BASEFLOW TO STREAMS AND RIVERS

High radon activities typically occur in surface waters near to where groundwater discharges to streams. Radon is a naturally occurring gaseous isotope sourced from geological formations whose activity rapidly declines within surface water due to gaseous exchange with the atmosphere and radioactive decay. However, there are uncertainties associated with quantification of the gas exchange co-efficient and the possible source of radon from river bed sediments (in the hyporheic zone), which may falsely indicate regional groundwater discharge to streams.

Studies along the Cockburn River, southeastern Australia, detailed in Report 2 Field Studies, investigated the use of radon and EC to quantify groundwater discharge to streams, and the use of an injected tracer experiment (SF6) to assist in showing the rate at which gases are lost from surface water in the absence of other processes.

The Cockburn River study shows that groundwater baseflow likely commences at river reach distance of 10 km (radon activity and EC increase from this point). At river reach distance of around 17 km radon activity ceases to increase and begins to decline, suggesting that there is no groundwater discharge to the river for a short distance downstream of this point. Comparison of radon activity and SF6 concentration decline shows the rate of decline in radon activity approximates the rate of decline in SF6 concentration between the river reach distance of approximately 17.5 to 18.5 km (EC increase also stabilises along this reach), confirming that baseflow is unlikely to be occurring along this reach of river. Downstream of 20 km, radon activities decrease but the rate of decrease is less than the rate of decline in SF6 concentration. EC also increases in this part of the River, confirming that groundwater discharge is occurring.

Figure CS.7 Plots of EC, radon activity and SF6 concentration vs. river distance (Cockburn River, NSW)


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6.3 Step 2.2; Threat analysis

Threatening processes are those that have the potential to reduce the biodiversity and ecological integrity of a regional ecosystem (Queensland Environmental Protection Agency, 2005). In terms of GDE water requirements, threatening processes are those that have the potential to reduce GDE access to water in terms of the key attributes of head/level, flux/pressure and quality.

Examples of threatening processes having the potential to impact directly upon GDEs include groundwater pumping (water table decline), land-use change (e.g. recharge reduction / increase, and GDE removal), changes in groundwater quality (e.g. salinisation, temperature and toxic chemical pollution), and surface water diversions (e.g. periods of inundation).

Examples of threatening processes that have the potential to impact indirectly upon GDEs include pest and weed invasion, urbanisation, climate change, disease (e.g. dieback) and natural disasters. Whilst most water planning activities do not focus on these indirect threatening processes it is important that any GDE threat analysis consider these processes and incorporate the results of any investigations within the framework for defining EWRs for GDEs. For example, the question may be asked “is the presence of weeds and pests causing a loss of GDE function, or is the altered water regime in which the GDE occurs a major contributing factor to weed and pest invasion?”.

Carefully defined EWRs form the basis for determining management strategies that consider the likelihood of reduced water availability in association with GDE threatening activities. The most important factors to consider in an analysis of threatening activities include:

• potential loss of biodiversity (consequence);

• the frequency (or probability) of ecosystem water shortage occurring in response to groundwater affecting activities, e.g. how often will access to groundwater be important in meeting plant water requirements; and

• whether there are physiological responses within ecosystem components that can compensate for possible water shortage, eg. reduced LWPs.

Any assessment of the potential for threatening activities to impact adversely on GDEs should, where possible, consider the risk posed to water availability by the threatening activity (see Case Study #1 and #4).

Changes in land-use (such as urbanisation), groundwater pumping and surface water diversions can:

1. Cause groundwater levels to gradually decline below the maximum rooting depths of terrestrial vegetation, and the hyporheic zone beneath ephemeral watercourses and wetlands. If there is insufficient water stored in the unsaturated zone (soil water reservoir) or if root

STEP 2.2

Threat analysis Purpose: To adequately provide for ecosystem water requirements it is necessary to understand those processes that threaten ecosystem access to water and how vulnerable they are to altered water regimes.


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morphology prohibits plants from accessing soil water stores (i.e. vegetation cannot adapt to an alternate source of water) at critical times associated with the type of dependency (continuous, seasonal or sporadic), GDE function can be expected to deteriorate. Groundwater pumping can cause rapid declines in groundwater levels that outpace rates of root elongation, even if groundwater levels do not decline below maximum rooting depths.

2. Reduce inundation regimes in wetlands, and watercourses and their anabranches, thereby altering ecosystem access to open water bodies in regard to both depth and frequency. In many cases, Australian wetlands and anabranch systems rely on surface water inundation following wet periods, with groundwater being an important water source between flood events. In these instances, groundwater can form a primary source of water to wetlands and in-stream ecosystems or serves to buffer water quality against the evaporative concentration of salts.

Widespread replacement of native vegetation with lower water use crops, irrigated agriculture or non-perennial pastures has increased recharge rates to many Australian groundwater systems. This has resulted in rising groundwater levels, the mobilisation of salts (that were formerly stored below the root zone of native vegetation) and subsequent increases in groundwater salinity and salt loads delivered to wetlands and streams that have a groundwater component to their natural water regimes.

Rising groundwater levels as a result of enhanced recharge, for whatever reason, can potentially cause the degeneration of terrestrial vegetation communities that are adverse to periodic or prolonged exposure to groundwater (waterlogging). The response of terrestrial, wetland and river baseflow GDEs to rising groundwater levels will depend on the inundation and salt tolerance of the component species and whether water inundation occurs during periods of active growth (high impact) or dormancy (low impact). However, in natural systems high groundwater levels generally coincide with periods of active growth (Naumburg et al., 2005).

Increased groundwater salinity levels create an osmotic gradient that makes it more difficult for plants (particularly salt-sensitive species) to extract water from soil. Plants can adjust to increasing groundwater salinity by increasing their tissue solute concentrations thereby creating an osmotic gradient that transports soil water / groundwater to roots (from higher to lower potentials). There is, however, a limit to the osmotic adjustment that plants can make and increasing groundwater salinity (lowering the osmotic potential) will ultimately result in plant water deficiency even though groundwater is available.

Changes in groundwater quality may also cause a reduction in GDE ecological function by: (a) increasing concentrations of naturally occurring elements to toxic levels; (b) introducing toxic substances; or (c) reducing the concentration of essential nutrients. Other pollutants that are toxic to ecosystems have been introduced to groundwater systems (such as herbicides) due to inappropriate usage or management practice, but the extent of this issue and its importance is presently not widely understood. Apart from the osmotic effect associated with increasing groundwater salinity levels, direct uptake of groundwater may prove toxic to plants due to excessive concentration and absorption of individual ions. Further, the salinity tolerance of species may be vastly diminished if changes in groundwater salinity occur abruptly rather than gradually.


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Table 6.3 presents tools and methods that might be useful in developing an understanding of threats posed to GDEs and incorporating a “risk” approach to developing environmental response functions (ERFs) from which to derive EWRs. A key consideration in all cases is the identification of obligate or facultative groundwater dependence, and what levels of management may be required to mitigate any adverse effects associated with identified threatening processes.

6.4 Step 2.3; Environmental response functions

From an ecological perspective, the term environmental response function (ERF) is used to describe the ecological response of an ecosystem, or a biophysical component of an ecosystem, to a given input. Typically, in GDE studies, ERFs have been used to describe, at a conceptual level, the relationship between ecological function (eg. condition or health) and groundwater availability (e.g. water table depth, salinity). Figure 2.1 presents a conceptual ERF.

Where the available data (existing or newly derived) allow a semi-quantitative or quantitative ERF to be developed for a particular GDE the understanding of GDE relationships with groundwater is further developed, thus providing a sound basis for deriving defensible EWRs.

To develop a detailed ERF, temporal observational data relating to ecological function and altered water regimes is often necessary. This would ideally require a number of field sites at which assessments of changes in ecosystem function following reductions in water availability have been made. Unfortunately there are very few sites in Australia where sufficient temporal data exist to allow a qualitative assessment of the impact of altered water regimes on GDEs and, consequently, very few studies have actually described an ERF in biophysical terms. Perhaps the most documented group of studies addressing this aspect of GDE water requirement determination are those relating to vegetation response to water table decline as a result of groundwater pumping from the Gnangara (groundwater) Mound, which is located on the Swan coastal plain in Perth, Western Australia. For example:

• Zencich et al. (2002) related Banksia transpiration response to water table depth on the Swan coastal plain;

• Groom et al. (2000) found that water table decline was accompanied by changes in Banksia community composition, floristic structure and, in some cases, increased mortality of canopy trees where water table drawdown was substantial; and

• Froend and Drake (2006) provides details of ERFs developed for Gnangarra Mound Banksia vegetation (see Case Study #8).

Environmental flows, that are considered protective of in-stream aquatic ecosystems, have been determined for many Australian rivers and streams. However, many of these studies have not explicitly considered groundwater baseflow contributions to maintenance of these environmental flows, and so do not necessarily protect in-stream ecosystems from the impact of groundwater threatening activities. Ideally, ERFs for stream baseflow and wetland GDEs will be developed to also consider surface water – groundwater interaction and so assess ecosystem resilience to changes in groundwater availability and/or quality.

STEP 2.3

Environmental response functions

Purpose: ERFs describe the relationship between GDE function and water availability. They form an important step in deriving EWRs.


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Table 6.3 Tools to assist in threat analysis

Code Tool Example methods T1 Mapping General

• key exercise in identifying the existence and location of threatening activities / processes

• mapping techniques provide the opportunity of assessing the proximity and extent of threatening activities to GDEs, and provide the basis to qualitatively assess the level of threat posed

• the results of analysis using other tools (eg. T2, T11) can be presented as mapping products and used to assist in conceptual modeling (T12)

T2 Water balance General • water balance approaches can be used to assess the extent to which an area’s water budget will change as the result of

threatening activities, such as groundwater pumping or water importation for pumping

• the results of the water balance can then be combined with other tools to assess the overall impact, eg. T10, T11 and T12

• models need to assess how aquifer / water body storage will change (δs) in response to changes to the amount of water entering (Inwater) or leaving (Outwater) a groundwater catchment (Inwater = Outwater ± δs), which manifests itself in either a rising or falling water table, or ponded water

• combining water balance terms with salt concentrations allows a salt balance to be developed (Insalt = Outsalt ± δC; where δC is change in concentration) to assist in assessing the potential for a changed groundwater salinity regime to impact adversely on terrestrial vegetation (Canadell et al, 1996)


General • observed ecosystem responses to historic water regimes (including salinity levels) can assist in assessing how GDEs might

respond to longer term alterations to the “natural” water regime

• extrapolating observations from other groundwater catchments can assist in developing an understanding of how ecosystems may respond to threatening activities, and their vulnerability (resistance and resilience) to change

• can provide a strong indication of obligate or facultative dependence

T6 Groundwater – surface water hydraulics

Wetland / stream baseflow GDEs • analysis of the likely change to hydraulic gradients in response to threatening activities will provide an indication of the scale of

reduced groundwater discharge, incorporate with T11 and T14


Wetland / stream baseflow GDEs • identifying zones / reaches of groundwater discharge will provide an indication of what GDEs are exposed to threatening activities

T8 Analysis of water chemistry

General • tolerance to altered salinity regimes is likely to be a major consideration for any threatening activity, incorporate with T2 and T11


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Table 6.3 Tools to assist in threat analysis (cont.)

Code Tool Example methods T10 Plant water use

modeling Terrestrial GDEs • the impact of reduced soil water or groundwater availability on terrestrial GDEs can be assessed by plant water use models such

as that described Case Study #9

• the results of studies similar to that described as Case Study #4 can provide an assessment of plant vulnerability to reduced water access


General • groundwater models provide an opportunity to assess the level of groundwater drawdown (removed groundwater access) that

might occur in response to groundwater pumping or recharge reduction, for example

• groundwater models also provide an opportunity to assess the level of groundwater discharge to surface water systems (removed groundwater access) that might occur in response to groundwater pumping or recharge reduction, for example

Terrestrial GDEs • soil water models can also provide a basis for assessing how certain threatening activities might impact on the soil water reservoir,

which will often form a critically important component of GDE “natural” water regimes

• the results can be incorporated with other tools to assist in assessing GDE vulnerability to change, particularly T10


General • the various tools described here for undertaking threat analysis can be used to develop conceptual models of GDE response to

threatening activities


Wetland / stream baseflow GDEs • identification of obligate aquatic GDEs in areas that may be adversely impacted by threatening activities / processes will be

important, incorporate with other tools (eg. T6, T8 and T11)


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CASE STUDY #8 – PHREATOPHYTE RESPONSE TO REDUCED WATER AVAILABILITY

In terms of terrestrial GDEs groundwater often forms only part of overall ecosystem water requirements. This will especially be the case where rainfall is seasonal and the soil water store has the potential to be regularly replenished. Where there is insufficient soil water to meet plant water requirements (either seasonally or annually), plants that can access groundwater will become increasingly dependent on that water source as the soil water store is depleted. In these situations, there is a risk of plant water stress occurring if for some reason (eg. groundwater pumping) the water table is in decline and dependent vegetation cannot extend their root systems to maintain contact with the capillary fringe.

Froend and Drake (2006) presented the results of a study to assess the response of Banksia woodland species to groundwater drawdown. The researchers developed a response function that related percentage loss of plant conductance (PLC), the ability of a plant to move water along water conductance pathways (principally the xylem vessels), and risk of tree mortality to drawdown, as represented by altered xylem water potentials (Ψx). The research outcomes are a crucial step in quantifying the critical ecophysiological response ot Banksia woodland to reduced water availability.

Figure CS.8 ERF for Banksia menziessi (b) and Melaleuca preissiana (d), relating xylem function (maintenance of plant water conductance pathways) to water availability. The plots show that for B. menziessi there is an approximate PLC of 20% for a Ψx of -2 MPa, and for M. preissiana there is an approximate PLC of 60% for a similar Ψx, indicating M. preissiana is less drought tolerant than B. menziessi, consistent with their status as obligate and facultative groundwater users.

Where temporal observational data are not available, other approaches are required to predict the impact of reduced water availability on GDE function. Obviously, from a management perspective, it will not always be desirable or possible to allow GDEs to become stressed so that observational data can be collected. In these cases, predictive modeling approaches can be crucial in defining ERFs for GDEs that may be impacted, or are being impacted, by threatening activities. Depending on the type of GDE being modeled, certain input data will be required to ensure the model predictions are representative and not based on conjecture. The toolbox and Framework provide the background to ways in which these datasets can be collected.

Cook and O’Grady (2006) describe one such approach for terrestrial vegetation known to be groundwater dependent to some degree. Their approach allows field measurements of depth to water table, plant water use, LWP and soil matric potential to be used in developing a calibrated predictive model of plant water conductance. Reducing soil matric potential values in the model


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are akin to what would occur in conjunction with water table decline, resulting in a reduced hydraulic gradient between the soil and leaf and a decrease in transpiration. The method has been employed by Howe et al. (2006) in relating plant transpiration response and leaf water potential to water table drawdown (Case Study #9).

CASE STUDY #9 – PLANT WATER USE MODEL FOR DEVELOPING PHRETOPHYTIC TERRESTRIAL VEGETATION RESPONSE FUNCTIONS

Water extraction by vegetation is often assumed to be proportional to the difference between leaf water potential and soil water potential. Leaf and soil water potential are both negative, but where leaf water potential is more negative than soil water potential there is an upward gradient that can drive water movement through the plant. As the water table declines, soil water potentials also decline (i.e. they become more negative) and the pressure differential driving plant water uptake reduces.

Howe et al. (2006) reported the results of plant water use modeling that simulated plant transpiration response to reduced water availability (water table drawdown). Model input parameters included soil matric potential profiles, root distribution and leaf water potentials. Stable isotopes were used to determine vegetation rooting depth. The model conservatively assumed that leaf water potentials and root distribution do not change in response to reduced water availability, and so the reduction in transpiration is proportional to the reduction in water potential difference between the leaf and the soil (see Cook and O’Grady, 2006 for model details).

Figure CS.9 ERF for Melaleuca viridiflora showing predicted rate of transpiration in response to a declining water table. The model demonstrates that M. viridiflora has a much reduced water availability, with transpiration rates predicted to reduce by 50% if the water table is allowed to decline by 1 m or more.

In the short history of GDE water requirement studies, most attention has focused on access to water (eg. water table depth and flux). To date, very little attention has been paid to ecosystem response to changing water quality regimes (salinity, nutrients, herbicides etc.). Whilst acute toxicity of some species of aquatic biota to salinity has been established, this is not necessarily the case for terrestrial vegetation. In addition, increased salt concentrations below toxic levels can be expected to disrupt normal ecosystem function. Future research will need to address this gap in our understanding of GDE water regimes.

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6.5 Step 2.4; Derive/refine EWRs for GDEs

In an environment where groundwater resources are relatively un-impacted by water affecting activities, and there is temporal data available for assessing ecosystem response to naturally induced changes to groundwater / soil water / surface water regimes, it is possible to determine the natural water regime within which a GDE operates. In the true sense of the term, this water regime can be regarded as the EWR, i.e. the water regime that provides for the ecological function of the GDE and the maintenance of biodiversity and ecological significance of the ecosystem. It is important to note, however, that these natural water regimes are dynamic and GDEs will demonstrate a degree of resistance and resilience (Hart et al., 2003) to varying water availability within that regime. In the case of:

• terrestrial GDEs this will typically relate to water table depth and groundwater salinity;

• baseflow systems this will relate primarily to flux and salinity; and

• wetlands this will vary depending on the form of dependence (level, flux, quality).

Historic groundwater conditions (water table depth and groundwater salinity) can be used to describe, at a very basic level, the ERW of a terrestrial GDE. The approach involves identifying the typical range of water table / salinity fluctuation observed in the past, ideally in conjunction with assessments of ecosystem condition (eg. leaf area, LWP), consistent with T5 (system response to change). The approach has been undertaken in the past where very little eco-physiological data have been available to support any other approach (eg. URS, 1999). The limitations of this approach, however, is that no allowance is made for the contribution of other water sources to the terrestrial GDE “natural” water regime, soil water in particular. These types of approaches are best supported by a likelihood analysis, where the probability of water shortage in a typical year is analysed to: (i) assess how often groundwater will likely be crucial in meeting plant water requirements (i.e. determine the degree of groundwater dependence); and (ii) assess the risk of additional plant water shortage in response to water table drawdown or salinisation. T2 (water balance modeling; Case Study #4) provides a basis for this analysis in the absence of actual data.

In those environments where groundwater resources are developed to some extent it may be impossible to describe to any great accuracy the EWR of GDEs largely due to the lag-time effect between the onset of groundwater affecting activities and ecosystem response, i.e. ecological processes observed today may relate more to prior groundwater resource condition then to existing condition (see figure 2.2).

Essentially, the development of appropriate EWRs requires consideration of all of the available data concerning ecosystem response to reduced access to groundwater (level, flux and /or quality), be it as a result of depleted soil water reservoirs or lower water tables/hydraulic gradients, or salinity changes. Because of the often large data requirements, this approach to developing EWRs has not been widely adopted. One example, however, is that taken by the Queensland Department of Natural Resources, Mines and Water in the Pioneer Valley, where

STEP 2.4

Derive / refine EWRs for GDEs

Purpose: We must understand the natural water regime (groundwater, soil water, surface water) within which GDEs exist if we are to appropriately manage GDEs to ensure their persistence in the landscape.


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water balance modeling (based on climate data, measured plant water use and PAW) was used to develop EWRs for terrestrial vegetation (Howe et al, 2006 - see Case Study #9).

In terms of salinity, decreasing salt concentrations in groundwater may be as equally deleterious to ecosystem function as increasing salt concentrations might be. This is because the change may allow species replacement to occur or impact on the manner in which plants access groundwater.

In terms of wetland and stream baseflow systems, the opportunity to build from environmental flow studies for EWR determination should be paramount. The ecological assessments undertaken for environmental flow studies provide a very sound basis for deriving EWRs for stream baseflow and wetland GDEs providing additional work (eg. baseflow separation; see T6) is undertaken to assess the timing and quantity of groundwater contribution to the water regime of these ecosystems.


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7 MONITORING AND EVALUATION

7.1 Monitoring Implementation of formal monitoring programs designed to measure defined ecological objectives are an essential component of any activities associated with developing EWRs for GDEs. Effective monitoring programs require the measurement of adopted performance indicators (eg. leaf water potentials and depths to groundwater), the complexity of which will be linked to available budgets, level of perceived threat to GDE function and conservation significance of GDEs in question.

7.2 Evaluation One of the more important aspects of implementing an environmental monitoring program is the review (or evaluation) process, which essentially involves comparing the condition of the ecosystem and its biophysical setting against environmental targets (ecological objectives) and baseline data. As a result, formal evaluation of the success of management strategies in protecting GDEs will be required within appropriate management timeframes, which are contingent of the degree of existing or planned groundwater development and the degree of threat posed to ongoing GDE function by water affecting activities (including groundwater, surface water and soil water, depending on the form of groundwater dependence that exists for GDEs).

In terms of management timeframes, it may be necessary to implement an evaluation process that is cognizant of the vulnerability of GDEs to changed water regimes. For example, terrestrial GDEs in areas where the water table is more than 5 m deep might warrant longer evaluation timeframes than riparian GDEs, where water tables are much shallower.


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ARMCANZ. 1996. Allocation and use of groundwater – A national framework for improved groundwater management in Australia. Agriculture and Resource Management Council of Australia and New Zealand, and Standing Committee on Agriculture and Resource Management.

ANZECC and ARMCANZ. 2000. Australian and New Zealand guidelines for fresh and marine water quality. Australian and New Zealand Environment and Conservation Council, and Agriculture and Resource Management Council of Australia and New Zealand.

Arthington AH, SO Brizga, MJ Kennard. 1998. Comparative Evaluation of Environmental Flow Assessment Techniques: Best Practise Framework. LWRRDC Occasional Paper 25/98. Land and Water Resources Research and Development Corporation (LWRRDC): Canberra.

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Boulton A. and PJ Hancock. 2006. Rivers as groundwater dependent ecosystems: a review of degrees of dependency, riverine processes and management implications. Australian Journal of Botany. 54(2): 133-144.

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Brizga SO, A Arthington, S Choy, N Craigie, S Mackay, W Poplawski, B Pusey and G Werren. 2001. Environmental flow report. Pioneer Valley Water Resource Plan. Queensland Department of Natural Resouces and Mines.

Canadell J, RB Jackson, JR Ehleringer, HA Mooney, OE Sala and ED Schulze. 1996. Maximum rooting depth of vegetation types at the global scale. Oecologia 108(4): 1432-1939.

Clifton C and R Evans. 2001. Environmental water requirements of groundwater dependent ecosystems. Environmental flows initiative technical report no. 2. Commonwealth of Australia, Canberra.


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Clunie R, T Ryan, K James and B Cant. 2002. Implications for rivers from salinity hazards: A scoping study. Report produced for the Murray-Darling Basin Commission, Strategic Investigations and Riverine Program – Project R2003. Department of Natural Resources and Environment, Heidelberg, Australia.

Cook PG and AP O’Grady. 2006. Determining soil and ground water use of vegetation from heat pulse, water potential and stable isotope data. Oecologia 148(1): 97-107.

Cook P, AP O’Grady S Lamontagne and P Howe. 2006. Pioneer Valley Groundwater Consultancy Report 2 identifying groundwater dependent ecosystem condition and processes. Prepared for the Queensland Dept. of Natural Resources, Mines and Water.

Council of Australian Governments. 1994. Water reform framework. Extracts from Council of Australian Governments: Hobart, 25 February 1994 communique.

Daily G. 1997. Nature’s services: societal dependence on natural ecosystems. Washinton D.C.

DLWC. 2002. The NSW State Groundwater Dependent Ecosystems Policy. Prepared for NSW Department of Land and Water Conservation by PPK Environment and Infrastructure. Ref. HO/10/00.NSW.

Eamus D and R Froend. 2006. Groundwater dependent ecosystems: the where, what and why of GDEs. Australian Journal of Botany, 54(2): 91-96.

Eamus D, R Froend, R Loomes, G Hose, and B Murray. 2006. A functional methodology for determining the groundwater regime needed to maintain the health of groundwater-dependent vegetation. Australian Journal of Botany, 54(2): 97-114.

Erskine WD, GW Begg, P Jolly, A Georges, AP O’Grady, D Eamus, N Rea, P Dostine, S Townend and A Padovan. 2003. Recommended environmental water requirements for the Daly River, Northern Territory, based on ecological, hydrological and biological principles. National River Health Program Environmental Flows Initiative Technical Report 4. Supervising Scientist Report 175, Darwin.

Froend R and PL Drake. 2006. Defining phreatophyte response to reduced water availability: preliminary investigations on the use of xylem cavitation vulnerability in Banksia woodland species. Australian Journal of Botany. 54(2): 173-179.

Groom PK, RH Froend and EM Mattiske. 2000. Impact of groundwater abstraction on a Banksia woodland, Swan Coastal Plain, Western Australia. Ecological Management and Restoration 1, 117-124.

Groom PK. 2004. Rooting depth and plant water relations explain species distribution patterns within a sandplain landscape. Functional Plant Biology. 31(5): 423-428.

Haase P, FI Pugnaire, EM Fernández, J Puigdefábregas, SC Clark and LD Incoll. 1996. An investigation of rooting depth of the semiarid shrub Retama sphaerocarpa (L.) Boiss. By labelling of ground water with a chemical tracer. Journal of Hydrology. 177: 23-31.


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Hamersley Iron. 1992. Marandoo Iron Ore Mine and Central Pilbara Railway environmental review and management programme overview. February 1992.

Hart BT, PS Lake, JA Webb and MR Grace. 2003. Ecological Risk to Aquatic Systems from Salinity Increases. Australian Journal of Botany. 2003. Vol. 51. pp 689-702. CSIRO Publishing.

Hatton T and R Evans. 1998. Dependence of ecosystems on groundwater and its significance to Australia. Land and Water Resources, Research and Development Corporation. Occasional Paper No. 12/98.

Holland KL., SD Tyreman, LJ Mensforth and GR Walker. 2006. Tree water sources over shallow, saline groundwater in the lower River Murray, south-eastern Australia: implications for groundwater recharge mechanisms. Australian Journal of Botany. 52(2): 193-205.

Howe P, PG Cook and AP O’Grady. 2006. Pioneer Valley Groundwater Consultancy Report 3 analysis of groundwater dependent ecosystem water requirements. Prepared for the Queensland Dept. of Natural Resources, Mines and Water.

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Kefford BJ, PJ Papas and D Nagged. 2003. Relative salinity tolerance of macroinvertebrates from the Barwon River, Victoria, Australia. Marine and Freshwater Research 54: 755 – 765.

Lamontagne S, AL Herzceg, JC Dighton, JL Pritchard, JS Jiwan and WJ Ullman. 2003. Groundwater – surface water interactions between streams and alluvial aquifers: Results from the Wollombi Brook (NSW) study (Part II – Biogeochemical processes). CSIRO Land & Water Technical Report 42/03. 64 p.

Mensforth LJ, PJ Thorburn, SD Tyerman and GR Walker 1994. Sources of water used by riparian Eucalyptus camaldulensis overlying highly saline groundwater. Oecologia 100: 21-28.

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Nielsen DL, MA Brock, GN Rees, and DS Baldwin. 2003. Effects of increasing salinity on freshwater ecosystems in Australia. Australian Journal of Botany 51: 655-665.

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9 GLOSSARY OF TERMS

Applied tracers Non-natural constituents that are intentionally introduced to a hydrologic system to characterise groundwater flowpaths and estimate velocities.

Aquifer A formation, group of formations, or part of a formation that contains sufficient saturated permeable material to yield economical quantities of water to wells and springs.

Aquitard A saturated but poorly permeable bed, formation, or group of formations that can store water but only yields it slowly to a well or a spring. An aquitard may transmit appreciable water to or from adjacent aquifers.

Baseflow That portion of stream flow derived from groundwater seeping into a stream.

Capillary zone The zone immediately above the water table, where water is drawn upward by capillary action.

Cone of depression A depression in the groundwater table or potentiometric surface that has the shape of an inverted cone, and develops around a well from which water is being withdrawn. It defines the area of influence of a well, spring or wetland.

Confined aquifer An aquifer that lies below low permeability material and where the piezometric surface lies above the base of the confining material, eg. artesian aquifers.

Digital elevation model (DEM)

A digital representation of the earth’s surface in terms of elevation values (X, Y, Z where Z represents the surface elevation).

Dissolved oxygen (DO) The measure of the amount of gaseous oxygen dissolved in an aqueous solution.

Drawdown

The distance between the static water level and the surface of the cone of depression.

Ecological services

The services and benefits that humans derive from ecological systems, including oxygen production, carbon stores and water purification.

Ecosystem

Term used to describe species in an environment and their relationship with one another and the non-living (abiotic) community.

Ecosystem services

Fundamental characteristic of ecosystems related to conditions and processes necessary for maintaining ecosystem integrity, which implies intact abiotic components (eg. soils and water), biodiversity and resilience to natural successional cycles (eg. fire, flooding, predation). Ecosystem function will include such processes as decomposition, nutrient cycling and production. It is generally considered that maintenance of biodiversity is integral to ecosystem function. The term is sometimes used interchangeably with ecosystem condition.

Eddy covariance

Technique that measures fine-timescale carbon and water fluxes between vegetation and the atmosphere.

Environmental water requirement (EWR)

Water regime needed to maintain a particular composition, structure and level of ecological function and ecosystem service provision. An EWR will either be the same as, or more than, an EWP.

Environmental flow Amount of water required by the environment (i.e. river system) to maintain ecosystem function.

Environmental water provision (EWP)

That water provided to the environment to sustain at least the basic function of ecosystems, whilst making allowance for economic and social interests.

Environmental response function (ERF))

The ecophysiological response of an ecosystem, or component of an ecosystem, to an altered water regime.

Geophysical surveys A process of searching and mapping the subsurface structure of the earth’s crust using geophysical methods such as seismic, magnetic, electromagnetic, gravity and induced polarization techniques.


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Facultative GDE Facultative GDEs require access to groundwater in some landscapes, but in

other landscapes can utilise alternate sources of water to maintain ecosystem function, i.e. the presence or absence of groundwater is not critical in determining ecosystem occurrence (compare with Obligate GDE).

Gaining stream A stream where baseflow, or groundwater discharge, serves to maintain and even increase stream flow as one goes downstream.

Groundwater The water contained in interconnected pores, gaps or fractures located below the watertable in an unconfined aquifer or located in a confined aquifer.

Groundwater dependant ecosystem (GDE)

Natural ecosystems that require access to groundwater to meet all or some of their water requirements so as to maintain their communities of plants and animals, ecological processes and ecosystem services.

Groundwater flow system

The total system which describes the movement of water in the subsurface from the point where it enters the ground to where it leaves. Water moves in the direction of decreasing pressure that may be upward in some localities.

Groundwater pumping tests

A test made by pumping a well for a period of time and observing the change in hydraulic head in the aquifer. A pumping test may be used to determine the capacity of the well and the hydraulic characteristics of the aquifer.

Ground-truthing The use of a ground survey to confirm the findings of an aerial survey or to calibrate quantitative aerial observations.

Hydraulic conductivity A coefficient of proportionality describing the rate at which water can move through a permeable medium. Horizontal hydraulic conductivity (Kh) refers to the coefficient of proportionality in the horizontal direction, whereas vertical hydraulic conductivity (Kv) refers to the coefficient of proportionality in the vertical direction.

Hydraulic gradient The rate of change in total head per unit distance in a given direction. The direction of gradient is that yielding the maximum rate of decrease in head.

Hydrograph A graphical representation of water level or discharge at a point on a stream as a function of time.

Gypsum blocks Measures soil water tension, a reflection of the force that a plant must overcome to extract water from the soil. Gypsum blocks measure tension in dry soil. Gypsum blocks consist of two electrodes embedded in a block of gypsum. The resistance between the two electrodes varies with the water content in the gypsum block, which will depend directly on the soil water tension.

Introduced tracers Dyes or conservative tracers that may be added to streams or aquifers to identify the occurrence and flux of discharging groundwater to river and wetland systems.

Laser scintillometry Measurement system for the determination of the turbulent fluxes of heat and momentum based on optical scintillation measurements.

Leaf area index (LAI) The ratio between the total leaf surface area of a plant and the surface area of ground that is covered by the plant.

Leaf water potential (LWP)

Measure of the water status of a leaf and hence the plant. A plant that is fully hydrated may exhibit a water potential close to zero.

Losing stream A stream where water is lost to the surrounding and underlying groundwater system as one goes downstream.

Major ions Constituents commonly present in concentrations exceeding 1.0 milligram per litre. Dissolved cations generally are calcium, magnesium, sodium, and potassium; the major anions are sulphate, chloride, fluoride, nitrate, and those contributing to alkalinity, most generally assumed to be bicarbonate and carbonate.

Matric potential The tension with which water is held to soil particles.

Model - conceptual Identifies hydrostratigraphic units and boundary conditions for a particular study area. Describes in simple terms how groundwater systems interact with other groundwater systems, surface water systems and ecosystems.


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Model – mathematical / numerical

Simulates groundwater flow indirectly by means of governing equations considered representative of the physical process occurring in the system, in addition to equations describing heads or flow along the model boundaries. Mathematical models can be solved analytically or numerically.

Neutron probes Neutron probes enable a rapid measurement of soil moisture to be made. The neutron probe has a radioactive source which releases neutrons. The neutrons are emitted into the soil when the probe is lowered into an aluminium tube which has been installed in the ground. Whenever a neutron collides with a hydrogen atom (part of a water molecule) it is slowed down. A detector counts the slow neutrons that have been deflected back to the instrument. A calibration equation is used to convert this number into a soil moisture content.

Obligate GDE Obligate GDEs are ecosystems that rely on groundwater for maintenance of some part or all of their ecosystem function. This reliance can be continual, seasonal or episodic. (compare with Facultative GDE).

Osmotic potentials Osmotic potential is the potential of water to move into a region by the process of osmosis, the potential of the water to travel from a hypotonic (low concentration) solution to a hypertonic (high concentration) solution.

Piezometer A non-pumping well, generally of small diameter, that is used to measure the elevation of the watertable or potentiometric surface. A piezometer generally has a short well screen through which water can enter.

Phreatophyte Plant that draws water from the saturated zone (i.e. below water table) to maintain vigour and function.

Potentiometric surface The level to which water will rise in wells screening a discrete aquifer. The water table is a particular potentiometric surface for an unconfined aquifer.

Radioactive isotopes Varieties of an element possessing the same chemical characteristics but emitting detectable radiation's by means of which they can be identified and traced.

Remote sensing Any kind of data recording by a sensor which measures energy emitted or reflected by objects located at some distance from the sensor (i.e. no direct ground contact).

Resilience - ecosystem Resilience relates to the capacity of an ecosystem that is adversely affected by a disturbance to recover to its prior condition (eg. for leaves to recommence normal rates of photosynthesis).

Resistance - ecosystem Resistance relates to the capacity of an ecosystem to resist change (eg. by ecophysiological means such as increasing leaf water potentials to overcome the effect of water table drawdown, or reducing canopy area to minimise transpiration rates).

Riparian zone Riparian zones are narrow strips of land that border creeks, rivers, lakes, or other bodies of water.

Sap flow techniques A direct measurement of plant water use using heat balance, heat pulse and thermal diffusion techniques. The heat balance sensor encloses the stem, while the heat pulse and thermal diffusion sensors require probes to be inserted into the plant stems.

Saturated zone The zone in which the voids in the rock or soil are filled with water. Sometimes referred to as the ‘phreatic’ zone.

Storativity The volume of water released from, or taken into, storage within an aquifer per unit surface area of the aquifer per unit change in head. In an unconfined aquifer, storativity is the same as specific yield.

Specific yield The amount of water that a unit volume of saturated permeable rock will yield when drained by gravity.

Stable isotope An isotope that does not undergo radioactive decay.


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Tensiometers A tensiometer measures soil moisture. It is an instrument designed to measure

the tension or suction that plants' roots must exert to extract water from the soil. This tension is a direct measure of the availability of water to a plant. A tensiometer consists of an air tight, water filled tube with a porous ceramic tip at the bottom and either a vacuum gauge at the top or a re-sealable rubber bung for a portable vacuum meter.

Time domain reflectometry (TDR)

Measures the bulk soil dielectric constant and electrical conductivity for simultaneous determination of soil moisture content and salinity. TDR works by embedding a parallel three pronged metallic probe into the soil. An electromagnetic pulse is launched along the probes, and the travel time and dissipation measured for the pulse to travel to the end of the probe and back again. The volumetric water content is calculated over a cylindrical volume of soil whose diameter is the distance between the prongs, and whose length is the length of the metal prongs.

Frequency domain reflectometry (capacitance technique) is similar to that of TDR in that the apparent dielectric of the soil is measured and empirically related to the moisture content. Measurement is undertaken by either lowering a sensor into the access tube or placing an array of sensors into the access tubes and logging the output frequency. The measured (angular) frequency is related to the soil moisture content via a non-linear calibration. Measurement of absolute moisture content is dependant on soil type and bulk density.

Total Dissolved Solids The total amount of dissolved solid matter found in a sample of water.

Transmissivity The rate at which water moves through a unit width of aquifer or aquitard under a unit hydraulic gradient. It is the product of aquifer thickness and hydraulic conductivity.

Transpiration The process by which water absorbed by plants, usually through the roots, is evaporated into the atmosphere from the plant surface, principally from the leaves.

Unconfined aquifer A water table aquifer.

Unsaturated zone The zone between land surface and the water table within which the moisture content is less than saturation (except in the capillary fringe) and pressure is less than atmospheric. Sometimes referred to as the vadose zone.

Water balance Balance of the water resources of a region, comparing precipitation and inflow with outflow, evaporation, and accumulation.

Ventilated chamber Measures transpiration by sampling the vapour pressure of air entering and leaving a plastic chamber enclosing a tree. The difference in vapour pressure between the two samples in used to calculate the transpiration rate.

Water table The surface between the unsaturated and saturated zones of the subsurface at which the hydrostatic pressure is equal to that of the atmosphere.

Well A borehole that has been cased with pipe, usually steel or PVC plastic, in order to keep the borehole open in unconsolidated sediments or unstable rock. Often used interchangeably with the term bore.


Appendix A

Existing Frameworks, policies and methods


A.1 Clifton and Evans (2001)

Clifton and Evans (2001) devised a conceptual GDE management framework comprising of four phases:

1. identify potential GDEs by developing an understanding of the form of ecosystem dependence on groundwater;

2. establish the natural water regime and level of dependence of the ecosystems in question;

3. assess the groundwater regime necessary to sustain the ecosystem’s water requirements (EWR); and

4. assess the impact that an altered groundwater regime will have on an ecosystem’s ecological function and devise necessary water provisions for GDEs.

The framework was designed to work within a range of operating environments, from those that are constrained by lack of information, budgets and resources to those that have a wealth of information, good budgets and adequate resources. Unfortunately, work undertaken to date in water allocation planning for GDEs has typically stalled at the desk-top GDE identification phase.

Clifton and Evans recommended in their report that further investment and research be undertaken nationally to identify GDEs, determine their conservation status, develop priority rankings based on this status and understand ecosystem response to altered water regimes.

Figure A.1 presents a summary of the Clifton and Evans framework. For further information the reader is encouraged to refer to the report.

A.2 DLWC (2002)

In 2003, the then New South Wales Department of Land and Water Conservation (DLWC) developed a rapid assessment process for identifying GDEs, their conservation value and appropriate management strategies. The process was adapted from the NCC (1999) desktop methodology. The essential features of this process revolved around identifying potential GDEs and their conservation value, identifying their vulnerability to changes in the natural water regime within which they exist, and then establishing appropriate management strategies to protect their important conservation values and ecological functions.

Identify potential GDEs

Dependency analysis

Natural water regime (EWR)

Assess response to altered groundwater

regime

Establish EWP

- groundwater dependent elements of ecosystem- key groundwater attributes- form of dependence

- dependent processes- patterns of groundwater use- water sources

Figure A.1 The essential features of the Clifton and Evans framework


An important component of the process was the need for review of the success (or otherwise) of implemented management actions, and the incorporation of research / investigations to address data and information gaps.

A.3 Pioneer Valley Groundwater Consultancy (2006)

The Queensland Department of Natural Resources, Mines and Water commissioned a consultancy in 2003 to assist with providing input to Pioneer Valley Water Resource Plan amendments with regard to appropriately allocating and managing Pioneer Valley GDEs. The three key objectives of the consultancy were to identify GDEs and assess their condition, develop an assessment framework to determine their water requirements, and assess the implications of future groundwater management strategies for GDEs.

The consultancy employed a broad range of tools and approaches to assist in addressing the objectives outline above, some of which were adapted from Clifton and Evans (2001) and DLWC (2002). The following presents a summary of work undertaken:

• An assessment of the biophysical setting within which potential GDEs exist (landscape, climate, vegetation occurrence, geology and soils, hydrology and hydrogeology), including GIS mapping.

• An assessment of biodiversity and conservation values for remnant vegetation.

• Field studies involving

- measurement of transpiration, leaf water potentials, soil water potentials, stable isotopes of groundwater / soil water and plant water;

- hydraulic studies, such as depths to groundwater, hydraulic gradients, baseflow separation.

• Development of GDE response functions, relating to soil water availability, water table drawdown, and baseflow reduction.

• Risk assessment of implications of altered water regimes for GDEs, and subsequent development of EWRs and EWPs.

• Preliminary development of monitoring and evaluation programs.

Further details of these studies can be found at (Queensland NRMW website address…) and Figure A.2 presents an overview of the assessment framework that was developed from the Pioneer Valley Groundwater Consultancy.


A.3 Eamus et al (2006)

In a recent publication that brings together recent research concerning GDEs (eg. the issues confronting water resource managers and policy makers), Eamus and others proposed a functional methodology for determining the “natural” water regime for phreatophytic vegetation. The methodology revolves around addressing four fundamental questions:

1. how can we identify species or species assemblages or habitats (GDEs) that are reliant on groundwater for maintenance of their persistence in the landscape;

2. what groundwater regime is required to ensure this persistence;

3. how can water resource managers, in particular, successfully manage GDEs with the resources at hand; and

4. what measures of ecosystem function can be monitored to ensure that management is effective?

Eamus et al. (2006) provides a step-by-step framework for addressing these questions. Figure A.3 presents a summary.

Identify study area

Identify biophysical setting

Identify possible GDEs

Identify GDE affecting activities

Establish relationship

between GDEs & groundwater

Assess impact of GDE affecting

activities

Derive EWRs for GDEs

Assess impact of changed

groundwater regime on GDEs

Derive EWPs for GDEs

Figure A.2 The Pioneer Valley EWR assessment framework


Identify groundwater dependent populations

or species within an ecosystem

Identify degree of groundwater dependency

Identify patterns of groundwater dependency

Identify groundwater dependent processes

Identify key groundwater attributes

constraining dependency

Identify changes to water regime that are

"safe"

Identify GDE response function to altered

water regimeDetermine EWRs

Figure A.3 Methodology for determination of EWRs as adapted from Eamus et al. (2006)

a framework for assessing the environmental water

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